Kei Nishikori, who was beaten by Cilic in last year's final, suffered a shock early exit, however, while there was also disappointment for Britain's Heather Watson as she crashed out at the first hurdle.
Find out how it all unfolded courtesy of Sports Mole's live coverage of the action below.
4.02pmGood afternoon! The start of the 2015 US Open is just a few minutes away as players involved in the opening matches as Flushing Meadows will be making their way out to the courts shortly.
4.04pmWe'll be bringing you the latest news, scores and results throughout the day, as well as game-by-game coverage of some of the biggest names in action, including Novak Djokovic, Serena Williams and Rafael Nadal. The first match we'll be focusing on though is Heather Watson's clash with Lauren Davis. The British number one is a former junior champion at Flushing Meadows, but has never won as a senior at the US Open. She's first up on Court 17 today.
4.06pmOn the big show courts, it's former world number one Ana Ivanovic who gets the action underway against Slovaki's Dominika Cibulkova, while last year's beaten finalist Kei Nishikori gets his campaign underway against Benoit Paire on Louis Armstrong Stadium.
4.09pmRight then, Lauren Davis and Heather Watson have just made their way out to Court 17. Interestingly, despite Davis playing in front of her home crowd, it was the Brit who got the biggest cheer, which suggests that the British fans may have turned up in force to cheer her on.
4.12pmWatson comes into this tournament ranked at 61 in the world. In her last Grand Slam tournament, the young Briton found herself a break up in the deciding set against world number one Serena Williams, but her opponent fought back to secure a narrow win in a thrilling Wimbledon encounter. Watson has never won a match at the US Open, and will be hoping she can end that run today.
4.14pmLauren Davis is making her fourth appearance at her home Grand Slam, having made her debut in 2011. She's never been past the first round, but has third-round runs at the Australian Open and Wimbledon under her belt. She's currently ranked slightly lower than Watson at 84.
4.16pmThis will be the first time that these two players have faced each other. Both have had quiet schedules since Wimbledon too, playing just a couple of matches since the start of the hard court season.
4.18pmRight then, the players are ready to go, with Watson serving first.
Davis *0-1 WatsonIt's a relatively straight forward start to the match for the British number one as Davis misses a couple of returns, before an ace gives Watson a 40-0 lead. Watson tenses up a little with a double fault, but the American's backhand is wayward again to hand the world number 61 the opening game.
Davis 1-1* WatsonWatson makes a couple of basic errors at the start of the game, hitting a forehand well long before missing the baseline with a backhand. There's a briefly troubling moment for Davis as her hair tie breaks, but she quickly adjusts her hair to play some well-timed grounstrokes, resulting in another error from the Brit.
Davis *1-2 WatsonWatson's serve looks really strong at the start of this match as she hits her second ace of the set, following it up with another service winner. Davis returns well to keep herself in the game, but the Brit soon seals it with another ace.
Davis 2-2* WatsonWatson's first return game wasn't great, and she tries to attack at the start of this with some excellent movement along the baseline, but edges her forehand just long again. She gets her first point against Davis's serve when the American misses a backhand, but Watson can only slice her forehand into the net while stretching to get the ball back, allowing Davis to keep the set on serve.
Davis *2-3 WatsonBoth players have been fairly cautious in the opening few games, focusing on keeping their serves tidy before putting to much effort into pushing for a break. It's the same in this game as Watson quickly takes a 40-0 lead before Davis gets herself into a rally, but the American's forehand goes long.
Davis 3-3* WatsonWatson comes inside the baseline to hit a superb forehand winner past her opponent, before a wide effort from the American gives Watson a 30-0 lead. It's the first time either player have really had a sniff against the other's serve. Watson brings up three break points when she hurries Davis, forcing her to hit her backhand into the net. The first goes begging as Watson hits one long, before Davis brings it back to 40-30 on the next point with a smash, while a couple of shots at the net take the game to deuce. It's Davis who brings up advantage when Watson tries too hard to keep herself in the game, hitting a forehand long again, before another wayward return hands the American the game. Davis showed impressive focus to get back into that one after falling 40-0 behind, Watson must be careful not to dwell on it too much though.
Davis *3-4 WatsonSo many times you see a player drop their serve after coming close to getting a break in the game before, but Watson quickly regains her focus to serve excellently again, keeping Davis at the back of the court as she struggled to get her returns in, before setting Watson up for an easy forehand winner.
4.52pmAt the change of ends, there's just time to update you on some of the scores from the other matches. 17th seed Grigor Dimitrov is already a set up against Australian qualifier Matt Ebden, while Agnieszka Radwanska has taken the first set in her match. Belgium's David Goffin is also in a hurry, taking the first set against Simone Bolelli, but there could be problems for fourth seed Kei Nishikori, as he's dropped the opener against Benoit Paire.
Davis 4-4* WatsonDavis makes a solid start as she watches Watson miss her first couple of returns, before the American record her first ace of the match. A sloppy backhand keeps Watson in the game briefly, but Davis seals it on the next point. There's been very little between the two players so far. Watson has looked the more dangerous on the return, but has also made more errors, while Davis has quickly settled into a solid rhythm.
Davis *5-4 WatsonBREAK! Watson makes a confident start as she fires an ace down the middle of the court, but Davis puts her under pressure with a couple of confident returns. Despite a second ace of the game from the British number one, Davis does enough to take it to deuce, the first time she has done so today. The American plays an excellent forehand down the line, which Watson gets her racquet on, but can only scuff her backhand into the net, bringing up a first break point of the match for Davis, which she takes as Watson blasts her backhand long.
Davis 5-5* WatsonBREAK BACK! Davis looks confident as she walks back out to serve for the opening set, but starts with a double fault. She soon finds her form again though, with two big serves in a row preventing Watson from getting inside the baseline. The Briton digs deep though, leaving Davis to hit her forehand long, giving Watson a chance to break back. It looks like the Brit is in control of the rally as she looks to level the set, but another mid-timed shot, this time on the backhand, goes long. At deuce, Davis ferociously strikes the ball from the baseline, clearly furious at herself for also letting her lead slip, but that results in a couple of errors, handing Watson the game. The Brit did play some good shots in that game, but it was the pressure affecting Davis that really decided it.
5.10pmElsewhere, Colombia'a Mariana Duque-Marino has become the first player to secure her place in round two, beating American Sofa Kenin 6-3 6-1 after just 58 minutes on court.
Davis *6-5 WatsonBREAK! Davis gives herself another chance to serve out the first set as Watson makes a double fault while 15-0 up. It seems to rattle the Briton as she makes yet more errors, which really have been the story of the first set for her, including a backhand which goes wide to hand Davis the game.
5.14pmFormer Wimbledon finalist Agnieszka Radwanska is also through to the second round, as she as eased to a comfortable 6-2 6-3 win over Katerina Siniakova of the Czech Republic.
Davis 6-6 WatsonBREAK BACK! After both players dominated on serve in the opening half of the this set, it's been a nervy few games, with Davis slicing her backhand wide and overhitting a groundstroke to give Watson two break points, which she claims as Davis mis-times a volley. This one's going to a tiebreak
TIEBREAK!Davis *6-3 Watson Davis's forehand clips the line. Watson challenges, but hawk-eye confirms that it was in, so it's set point for the American.
Davis 7-6 WatsonSET! Davis serves, and Watson gets her return back, but her next shot goes long, handing her opponent the opener. It was a long set, lasting 66 minutes!
5.28pmAs the players on court 17 take a break at the end of the set, there's a chance to catch up on the scores from elsewhere. Ana Ivanovic is in trouble, dropping the opening set against Dominika Cibulkova, but Nishikori is back in his match against Benoit Paire after winning the setting set. Grigor Dimitrov is closing in on a place in round two after winning his first two sets, while Russia's Ekaterina Makarova is through.
Davis 7-6 1-0* WatsonDavis makes a bright start to the second set, winning the opening point with an ace, before watching Watson miss a couple of backhands. Davis seals it with a well-directed serve out wide, which Watson can't get back across the net.
Davis 7-6 *1-1 WatsonWatson is quite as comfortable as her opponent was in her first service game of the second set, but she gets a hold, with some accurate serving forcing a couple of wide returns from her opponent, before the American overhits a backhand.
Davis 7-6 2-1* WatsonDavis's serve seems to have a bit of extra power behind it at the start of the second set, as she hits another ace, before following up a pacy delivery with a forehand winner. Watson fights to get back into it, using her pace along the baseline to get it back to 40-30, but a mis-hit forehand allows Davis to get the hold of serve.
5.42pmAna Ivanovic is back on level terms in her match against Dominika Cibulkova over on Arthur Ashe. Meanwhile, we told you that Ekaterina Makarova was through in straight sets a little while earlier. What we should have also told you is that she faces the winner of this match between Lauren Davis and Heather Watson in the second round.
Davis 7-6 *3-1 WatsonBREAK! Heather Watson seems to completely lose her focus, hitting a string of poor shots to give Davis two break points, and the American converts at the first time of asking, catching Watson out with a vicious return, which the Brit can only hit long. Davis could easily run away with this match is Watson doesn't find something extra soon.
Davis 7-6 3-2* WatsonBREAK BACK! Watson digs deep to get the second set back on level term, she really needed that game! at 15-15, Davis makes a double fault which gives Watson a chance, and she attacks from the back of the court to give herself two break points. The American saves the first with an ace, but a forehand error costs the 21-year-old. Great response from the British number one.
5.51pmBelgium's David Goffin is the first player in the men's draw to reach the second round. The 14th seed has beaten Simone Bolelli in straight sets. Read all about it here.
Davis 7-6 *3-3 WatsonWatson finally seems to be hitting her stride, coming into the net for the first time today to give her the first two points of the game, before some powerful serving forcing a long return from Davis. She seals it with it an ace.
Davis 7-6 4-3* WatsonWatson has had all the momentum in the last couple of games, but Davis serves well to make sure she keeps herself in the set. Watson has been struggling all day to pick out the baseline from the back of the court, and she misses again with a couple of long efforts, before Davis rifles a forehand down the sideline.
Davis 7-6 *4-4 WatsonWatson comes into the net to secure the opening point of the game with a volley, and seems to be heading for a comfortable hold as she opens up a 40-15 lead. Davis attacks from the back of the court with an excellent forehand winner, before Watson mis-cues, taking the game to deuce. Davis tries to hard to create a chance to break though, twice firing her backhand wide while looking for the sideline.
Davis 7-6 4-5* WatsonBREAK! Davis makes two double faults on her way to giving Watson a 40-0 lead, handing the Briton a chance to go a break up for the first time in this match. The American appears to have totally lost her service rhythm as she gifts Watson the game with a third double fault in four points. She's served so well up until this point, but the pressure of the occasion just seems to have go to her. Watson will serve for the set next.
Davis 7-6 *5-5 WatsonBREAK BACK! Davis hits a couple of superb forehands before Watson misses her backhand, giving the American the chance to break back, which results in some rather choice language from the British number one. She saves the first, serving well to force a long return from her opponent, but another wayward backhand gifts the game to Davis.
Davis 7-6 6-5* WatsonThe double faults are still a problem for Davis as she opens with yet another, after making three in her last service game. She quickly puts her struggles to one side though, battling in a rally to flick a forehand past the Briton, before watching her opening rifle the ball long. She's just one game off a spot in the second round now.
Davis 7-6 6-6 WatsonWatson looks calm as she rises from her chair after the change of ends, and secures the opening point with a confident volley at the net. Davis responds with a simply stunning forehand to the sideline though. Watson makes a solid forehand of her own to edge back ahead, before a long forehand from the American takes the set to a tiebreak again.
TIEBREAK!Davis 6-0* Watson Davis hits another forehand winner to give herself six match points.
6.29pmGAME, SET & MATCH! Lauren Davis 7-6 7-6 Heather Watson
6.30pmIt's another Flushing Meadows disappointment for Heather Watson! For the fifth year in a row she's out in the first round at the US Open, with young American Lauren Davis securing her first win at her home Grand Slam. She plays Ekaterina Makarova, who is seeded 13th, in the next round.
6.31pmIt was a clinical performance in the second tiebreak for the American. She served superbly during her own points, while really taking it to Watson on the return.
6.36pmElsewhere, Nishikori has come from a set down to lead France's Benoit Paire 2-1, while Jo-Wilfried Tsonga has taken the opener in his match against Jarkko Nieminen. Meanwhile, former champion Venus Williams is warming up for her match against Monica Puig on Arthur Ashe. That match will be underway shortly.
6.38pmThere's an interesting match taking place on the Grandstand court too, with American Mardy Fish facing Italy's Marco Cecchianato. Fish is retiring after this tournament, following a difficult couple of years with health problems. He lost the first set, but has fought back to lead 2-1.
6.42pmWorld number one Novak Djokovic will get his campaign underway later today, looking to secure his third Grand Slam title of the year. The Serbian was beaten in the finals of the Montreal and Cincinnati Masters by Andy Murray and Roger Federer respectively in the build up to this tournament, and admits that he isn't happy with his form. Just one of his nine Grand Slam titles to date has come at Flushing Meadows.
6.49pmJo-Wilfried Tsonga is now two sets up in his match against Jarkko Nieminen, while Jelena Jankovic, who is seeded 21st in the women's draw, is in control in her match against Oceane Dodin of France. 18th seed Feliciano Lopez made a slow start against unseeded Georgian Nikoloz Basilashvili, needing a tiebreak to secure the opening set. He's wasted no time doubling his lead though, winning the second set 6-1.
6.52pmSome of the women are racing through their first-round matches today. Estonia's Kaia Kanepi is the latest to book her place in round two, thrashing Anna-Lena Friedsam of Germany 6-1 6-1.
6.56pmOne match which is going the distance though is the clash on the Louis Armstrong court between Kei Nishikori and Benoit Paire. Last year's beaten finalist appeared to be in control after coming from a set down to lead 2-1, but the French fought back in a tiebreak to take it to a deciding set.
6.59pm2012 men's champion Andy Murray isn't in action today. He'll get his tournament underway when he faces the controversial Nick Kyrgios tomorrow. The young Aussie has been in the news for all the wrong reasons recently, earning himself a fine and a suspended ban for comments he made about Stanislas Wawrinka's girlfriend during a recent match. The Scot has been defended his opponent though, telling BBC Sport: "I don't think he's a bad guy. He's just got to learn a little bit and he'll be fine."
7.02pmGood news for the imminently retiring Mardy Fish - he's extended his career by at least one more match, coming from a set down to beat Cecchinato in four sets. He'll play either Feliciano Lopez or Mikoloz Basilashvili in the next round.
7.04pmThere's another thriller that's been slowly brewing on court 15, with Lithuania's Ricardas Berankis and Joao Sousa of Portugal heading into a fifth set. Berankis must have thought that he had it in the bag after racing to a two-set lead, but Sousa has fought back to force it into a deciding set.
7.07pmFormer British number one and US Open finalist Greg Rusedski has been working with Heather Watson this year. The 41-year-old has been speaking following her first-round exit in New York, and believes that she should have won the match.
7.12pmWe told you a little earlier about Mardy Fish extending his career with a win in the first round. Well, one man who has played his last Grand Slam match is Finland's Jarkko Nieminem. He's retiring at the end of the year, and has been beaten in straight set by France's Jo-Wilfried Tsonga.
7.15pmItaly's Andreas Seppi is through too, beating American teenager Tommy Paul 6-4 6-0 7-5. He'll face the winner of the match between Spain's Pablo Andujar and Teymuraz Gabashvili of Russia in the next round.
7.18pmTwo-time champion Venus Williams has had an eventful start to her match. She dropped her serve in the opening game of her meeting with Monico Puig, but has fought back to take a 5-4 lead.
7.25pmAmerica's Jessica Pegula has had a day she won't forget, winning her first ever Grand Slam match, beating Belgium's Alison van Uytvanck in straight set. She faced Dominika Cibulkova in the next round.
7.31pmThe completion of Nishikori's match means that defending champion Marin Cilic will get his campaign underway in the next few minutes. Nishikori and Cilic both pulled off upsets in the semi-finals last year, eliminating Novak Djokovic and Roger Federer respectively. The Croatian is the ninth seed at this year's tournament, and face Argetina's Guido Pella this evening.
7.34pmBenoit Paire had looked like a star of the future when he first broke into the top 20, but has had a difficult couple of years. He started well against Nishikori before the Japanese star hit back. Nishikori has had problems with injuries in the last couple of weeks, but Paire's fightback was still a huge surprise. You can read more about that match here.
7.37pmThere's some good news for the home crowd watching on court four, as America's Madison Brengle has survived a tricky tie with Sasai Zheng to progress to the second round. Brengle eased to the first set, but eventually game through 6-2 5-7 7-5, with the final set taking 85 minutes! She'll face compatriot Anna Tatishvili or Karolina Pliskova of the Czech Republic int he next round.
7.40pmIt's less than four hours since the first matches got underway, and we've already lost the fourth seed from the men's draw and the seventh from the women's singles. Now, it looks like another could be in trouble as 10th seed Carla Suarez Navarro is 3-0 down in the opening set of her match against Denisa Allertova. It's still early in the contest though, so she has time to fight back.
7.44pmThis will be the final year that players face the risk of a rain delay if they play in the Arthur Ashe Stadium. The tournament is in the process of fitting a roof to the main stadium, which is scheduled to be in place by next year. It's one of a number of developments taking place at Flushing Meadows, with the Arthur Ashe stadium being demolished after this tournament, and rebuilt for the 2017 edition.
7.47pmWhat is going on with the top seeds today?! Ana Ivanovic and Kei Nishikori are already out, and 10th seed Carla Suarez Navarro is trailing, now Karolina Pliskova is in trouble. The Czech, who is the eighth seed in the women's draw, lost the opening set 6-2 to unseeded American Anna Tatishvili.
7.50pmLithuania's Ricardas Berankis has finally booked his spot in the second round. He was 2-0 up against Portugal's Joao Sousa at one point, but neeed a fifth set to come through. He meets 14th seed David Goffin next.
7.53pmNot all of the seeds are struggling, as 10th seed Milos Roanic is a set up against Tim Smyczek. The Canadian has never been past the fourth round at the US Open, but has certainly made a strong start to this year's tournament.
8.13pmWe will be bringing you a live commentary of Novak Djokovic's clash with Joao Souza after Williams has rounded up her contest at the Arthur Ashe Stadium. Venus was just serving for the match against Puig, but lost the game to keep us waiting surely just a few moments longer. The American currently leads the second set 5-4.
8.18pmDjokovic will be looking to secure his third Grand Slam title of the year at this tournament. The Serbian has not been in the best of form heading into this offering, having suffered defeats in the Montreal and Cincinnati Masters finals before the US Open.
8.22pmPuig is doing all she can at the moment to fend off a victory from Venus Williams. The underdog drew level at 5-5 in the second set, but Venus has just moved into a 6-5 lead and will be looking to break serve in order to seal the match.
8.27pmThe supposed underdog holds out for now, then! Puig has moved the scores back to 6-6 in the second set to establish a tiebreak. Could she do this? We'll keep you posted as the extra period comes to its conclusion.
8.32pmRESULT! Anna Tatishvili has given the Americans something to smile about today. The unseeded 25-year-old has defeated Karolina Pliskova 6-2 6-1 to move into the second round of the tournament. Read our report of that contest here.
8.34pmBack to our main focus now, and Williams has just thrown away three match points against Puig in the tiebreak - they're now tied at 6-6 in the extra offering in the second set. Should Venus take this tiebreak, she'll win the game and progress into the next round.
8.40pmOh no, what has Venus done? She's thrown away the tiebreak despite having four match points at one point in the game. That fixture will be heading into a third and final deciding set. After that, it'll be time for Djokovic against Sousa.
8.54pmBenoit Paire must be in dreamland after battling back to steal that memorable win over Kei Nishikori earlier this evening. The Frenchman told fans about what he believed to be an "impossible" victory after overcoming the Japanese star. You can read what Paire has had to say right here.
8.59pmMilos Raonic is currently on course to claim a comfortable win over US native Tim Smyczek. As it stands, the Canadian leads his opponent 6-4 7-6 and is also ahead 3-0 in the third set.
9.02pmCroatian Marin Cilic is also ahead in his fixture with Guido Pella having won the first set 6-3. The pair have now entered into a tiebreak with the scores level at 6-6 in the second.
9.11pmWe could soon be headed for a final conclusion from the clash between Williams and Puig. Venus now leads the last set 4-2.
9.12pmGoing back to that Cilic game, the Croatian star has just taken the tiebreak to lead 6-3 7-6 and establish the chance to wrap up passage into the next round within three straight sets against Pella.
9.14pmRESULT! We have a conclusion in the women's draw as Denisa Allertova has just beaten Carla Suarez Navarro to move into the second stage. The 22-year-old has moved past the first round for the first time in her career with a 6-1 7-6 victory. You can read about that game here.
9.17pmRESULT! We had just been going through Raonic's game with Tim Smyczek, and the Canadian has now put the finishing touches to a 6-4 7-6 6-1 win over the American. More on that win over at this link.
9.24pmRESULT! Venus has finally put her game to bed against Puig. The two-time US Open winner has completed a 6-4 6-7(7) 6-3 win at the Arthur Ashe. More details here.
9.27pmSo next up we'll have full coverage of Djokovic's opening match at the tournament. Elsewhere, Radu Albot has just taken a first-set lead over David Ferrer.
9.34pmDjokovic and Sousa are due out in just a few moments time. The two players are yet to meet competitively before this contest and the Brazilian will do well to take a set off the world number one tonight.
9.36pmDjokovic last won this tournament in 2011 and has been in the finals four times since then! He'll be itching to claim a victory having been disappointed in the past few years. The players are now making their way out onto the court as we await the start of Djokovic's US Open campaign.
9.42pmThe players are just running through their final warmups before the start of the clash. World number one against number 91... Souza has never won a main draw match at Flushing Meadows.
9.45pmThis contest could be interrupted by some rain in the next hour or so, but let's hope it stays away so we can get through this fixture unchallenged. As it stands, weather experts predict a 30% chance of rain.
Djokovic 1-0* SouzaDjokovic begins impressively by forcing an error and then taking successive points with two blinding aces. The Serb closes out the game by forcing another error from Souza on the forehand.
Djokovic *1-1 SouzaSouza battles back off his own service as Novak can't help but lose out on two backhand returns. Souza continues to apply some pressure with a showing of power as Djokovic has no answers on his forehand, as he eventually surrenders the game with another two errors.
Djokovic 2-1* SouzaNovak is slowly growing into this after a couple of games and he comes back from an error to win cleverly on the forehand. Souza gets clumsy with a couple of mistakes, but comes back strongly at 40-30 with a brutal forehand. Djokovic eventually takes the game when Souza is forced to concede on the forehand.
Djokovic *3-1 SouzaBREAK! After a short stop, Souza is back on serve and he concedes by whipping long out the back of the court, before following it up with two more mistakes to go 40-0 down. Djokovic sense the chances and moves in to build some intensity, causing Souza to fail on the volley and concede the first break of the match as his shot goes long.
Djokovic 4-1* SouzaBack on service, Djokovic opens up with a forehand winner, but Souza responds to draw level at 15-15. A rare dodgy backhand from Novak then sees the Serb move behind in the scores only to come back into the contest with Souza unable to respond with his forehand. Djokovic then produces another standout ace to move ahead, before sealing the point when his Brazilian opponent is unable to counter down the line.
Djokovic *5-1 SouzaBREAK! Strong work on the forehand opens up the first point for Souza, but he then fails on the backhand. The Brazilian moves forward to the net and whips over to move back in front, only for Djokovic to reply with a pump short into Souza who fires a reply out wide. Another error from Souza sees Novak offered another break point, before his opponent draws deuce when Novak crashes into the net. More mistakes from Souza put Djokovic on the brink, and he eventually takes his break when Souza hands him an unforced error on the forehand.
Djokovic 6-1* SouzaSET! Djokovic opens up nicely with an ace and he soon takes the first set with relative ease after Souza produces an error before being unable to respond to another impressive ace. Novak puts things to bed by forcing the Brazilian into a poor charge on the forehand that fails to register.
Djokovic 6-1 *0-1 SouzaTwo impressive aces sees Souza take command in game one of the second set, with Djokovic struggling with a few forehand errors in the opening gambit.
Djokovic 6-1 1-1* SouzaDjokovic seems in good shape at the start of this tournament and he takes charge back on his serve by pushing Souza into a long return. After battling back from an irritating mistake, the Serb takes the game with two strong shots that push his opponent deep and into two errors.
Djokovic 6-1 *2-1 SouzaBREAK! Both players throw away poor chances early on as the scores move to 15-15, before Djokovic wins out on an important challenge on the long shot to take the lead. He cannot keep it, however, as Souza responds with a cheeky chip over the net. Things take a turn for the worse for Souza when he produces two needless errors, allowing Novak to capitalise when his return sees the Brazilian crunch poorly into the mesh.
Djokovic 6-1 3-1* SouzaAfter opening up poorly on his own service, Djokovic comes back into it with some adroit attacking that produces a clever forehand punch into Souza. Continued pressure tennis from the Serbian sees no answers from his opponent and Novak wraps up the game without response from Souza.
Djokovic 6-1 *4-1 SouzaBREAK! Neat service play from Souza allows him to force Novak into a costly error at 15-0, but the Serb pushes back with the help of two standout backhand winners that eventually put him into a 40-15 lead. Djokovic does not let up and eventually moves on to take yet another break as he witnesses Souza collapse with a backhand that results in a forced error. Novak is in total control...
Djokovic 6-1 5-1* SouzaNovak's service is looking great now as his second sees Souza only able to send a return that goes racing beyond the Serb's face and out. It's hard to decide what's best in this game, a wonderful ace to make it 40-0, or the stunning backhand winner that follows to conclude the point without any kind of resistance from Souza. Straight game that one!
Djokovic 6-1 *6-1 SouzaBREAK AND SET! Unforced errors open proceedings for the players at 15-15, but Novak comes good with another wonderful backhand. The Serbian is powerless to stop Souza's ace, before seeing his opponent produce a double fault to hand him another break point. The world number one willingly accepts and makes it two sets to nil when he wins on the challenge - much to the dismay of Souza who thought he had got away with a long one.
Djokovic 6-1 6-1 1-0* SouzaContinued progress then from Djokovic who looks on course to wrap this up without conceding a set. The Serbian moves into a 40-0 lead as he produces a standout smash to punish Souza midway through his assault. Souza replies with one point, but it is not good enough as Novak wins the game with an unstoppable ace.
Djokovic 6-1 6-1 *1-1 SouzaThis looks like it will be over pretty quickly, although the Brazilian now decides to impress with his best game of the match. Strong tennis on the serve followed by some dominant placement on his returns allows Souza to take game two of the third set with unheard of comfort compared to the rest of this encounter.
Djokovic 6-1 6-1 2-1* SouzaHope may not be lasting too long, however, given that Djokovic comes back to bludgeon his way through the third with some wonderful tennis on the backhand. He completes the game with a dominant showing on with a swipe that does for Souza.
Djokovic 6-1 6-1 *3-1 SouzaBREAK! Souza comes good despite the grim circumstances as he shows the crowd some flair to take the first two points on his forehand, but on cue comes up with a double fault to bring Djokovic back in. A backhand error into the net follows and sets up the break point, which Novak accepts with a bulleted backhand that sees Souza crash into the mesh once more.
Djokovic 6-1 6-1 4-1* SouzaThis could well be over within the hour as Novak races through another game with more punishing work on his service. Almost robotic brilliance from Novak, who seals the game with a crushing forehand to follow up a memorable ace earlier on in the third's fifth.
Djokovic 6-1 6-1 *5-1 SouzaBREAK! Hmmm, Souza only has himself to blame now as he comes up with two terrible unforced errors - first on the forehand into the net and then on the backhand into the same area. More class follows from Novak who pulls off a wonderful pump down the line to make it 40-15. Souza pulls one back, before Novak takes the break when his opponent spoons a forehand wide after a standout rally.
Djokovic 6-1 6-1 6-1* SouzaGAME, SET & MATCH! Lights out then for Souza who is unable to prevent Novak from sealing things off his own service. The world number one takes the match without conceding in the final game, with things being rounded up when Souza is unable to return on the forehand.
11.00pmRESULT! So there we have it, Djokovic marches into the second round without really having to break a sweat against Souza. The Brazilian looked all over the place in that contest. He gave far too much away to Novak, who seemed in no mood to stick around for any longer than he had to.
11.03pmWhile that contest was underway, Marin Cilic produced some dominant tennis to ease past Guido Pella in straight sets. You can read more about his victory here.
11.12pmWe mentioned a little earlier that Albot was one set up against Ferrer. Well, the Spaniard now finds himself two sets up with a 4-6 7-5 6-1 lead over the Moldovan. Can he do it? We'll keep you posted on that clash as it develops.
11.16pmRESULT! Albot has evidently collapsed in that fourth set as Ferrer has just taken it unopposed to claim a 4-6 7-5 6-1 6-0 victory over the 25-year-old. You can get all the necessary information from that contest with our own match report.
11.25pmIt has just been confirmed that Andy Murray's clash with Australian wonder-kid Nick Kyrgios will be the evening match tomorrow night in New York. Murray has been speaking about his opponent ahead of the game, and the Scot has insisted that the youngster "is not a bad guy".
11.42pmSerena Williams is due to begin her tournament at around midnight. Before that, here is some reaction from Djokovic's breezy win over Souza. The Serbian star has insisted that he has a chance of claiming the Open if he is able to keep up the form shown in his first-round win over the Brazilian tonight.
11.54pmOnce the contest between Williams and Vitalia Diatchenko is over, Rafael Nadal will be looking to get his year back on track as he prepares to face Borna Coric at the Arthur Ashe Stadium. We will be bringing you coverage of those contests as they develop in New York.
11.57pmEarlier this evening we saw a standout clash between Venus Williams and Monica Puig, which eventually ended in Williams winning out after a hard-fought battle. Following her victory, Williams has moved to heap praise on her opponent. You can read what the two-time champion has had to say here.
11.57pmThat is going to be all from me this evening. I will be leaving you in the trusted hands of my colleague Shane Callaghan...
12.08amThanks Chris. Morning folks. Day one is winding down, but it's far from over because we've still got Rafael Nadal and Serena Williams - who only have the eight US Open titles between the - to come so don't be going anywhere just yet. It's a big game for Nadal as he sets out on the road to prove he's still relevant, having endured a troubled 2015 it has to be said.
12.19amSET! There's no messing around from Gael Monfils, who cruises into a one-set lead over Illya Marchenko with a 6-2 scoreline. Serena Williams's first-round clash with Vitalia Diatchenko is just around the corner. She has only won the tournament every year since 2012. #Monopoly
12.22amVying for a clean sweep of Grand Slam titles, another US Open triumph would see her pick up a 22nd major title, which would see her tie with Steffi Graf, with the aptly-named Margaret Court the only player in history to top both of them. Serena's not bad at this tennis lark, is she?
12.29amEsteban Granero of Real Madrid and QPR fame is performing a musical number. On second thought, it might be Josh Groban. They look quite similar I'm sure you'll agree. We shouldn't be too far away now.
12.37amVanessa Williams now gives us a rendition of Star Spangled Banner, and now the organisers just have to free the court up of three singers, a full orchestra and the entire NY police force. If you ever wanted to commit a crime in New York tonight's the night because the cops are all packed into Flushing Meadows.
12.40amApart from the fact that her surname is tricky to pronounce, what do we know about Vitalia Diatchenko then? Well, she's Russian, 25, and has never progressed past the first round in this competition - and that game was way back in 2011. This could get ugly.
12.43amRESULT! Daria Kasatkina, who replaced the injured Maria Sharapova, has beaten Daria Gavrilova in her first ever Grand Slam match! I haven't come across the name Daria since that MTV cartoon ended, and now we see it twice. It's like waiting for a bus.
12.44amInterviewed by ESPN just before the match, Williams says that she has "nothing to lose". Has she momentarily forgotten who she is?
12.48amBoth players are on the court now as they rally the ball back and forth to warm up. Williams just gestured to the crowd to make some noise - and they oblige her.
12.49amDiatchenko has won a career total of $619,000 - and she's only 86th in the world. We're in the wrong business folks.
Williams *1-0 DiatchenkoThe world number one didn't waste much time drawing first blood, moving 30-15 ahead before Diatchenko incorrectly challenged an 'in' call and it was plain sailing for Williams from there. It could be a really short night for the Russian.
Williams 2-0* DiatchenkoBREAK! A really short night. Williams moves 2-0 ahead as three unforced errors from the Russian hand her American counterpart a two-game lead. Diatchenko has an unorthodox serve: no backlift, no grunt. It's a bit too effortless.
Williams *3-0 DiatchenkoWe may only be three games in but it's hard to ignore the prospect of a whitewash already. Williams pulls out three aces as her powerful serve is really causing Diatchenko problems in these early stages. She's 3-0 ahead inside seven minutes.
Williams 4-0* DiatchenkoBREAK! A double fault gives Williams a 15-0 lead, and two more unforced errors lead to a 40-0 advantage. This is too easy for her as she wins a fourth successive game. Diatchenko's needs a service coach. If she serves one ace this morning I'll be astonished.
Williams *5-0 DiatchenkoSpeaking of aces, Williams serves THREE to move 5-0 ahead. Three, before nonchalantly walking back to her seat. This can't even be considered sparring. It's ridiculously one-sided - through no fault of the Russian, who just isn't on the same level here unfortunately.
1.11amWe might have a problem as Diatchenko calls for the trainer, who seems to be examining the 25-year-old's foot. She is now officially receiving a medical timeout.
1.13amThere's a bin beside them, and god forbid it should be blow over because we've seen enough rubbish on that side of the court already. That's harsh. Williams is just on another level.
Williams 6-0* DiatchenkoBREAK and SET! Dare I suggest Diatchenko has called it a day? She commits TWO double faults en route to losing the first set 6-0, before just walking out off court! Who can blame her? Williams has served NINE aces, and the Russian has suffered FIVE double faults. She could still be suffering from that injury. Who knows.
1.20amDiatchenko is back on court, met by applause by the crowd who waited long enough to see this, and they want to see it finish. Here we go.
Williams *6-0 1-0 DiatchenkoDiatchenko loses the first game of the second set without winning a point, as she shanks Williams's return way out to the right. The American is five games away from a whitewash and, in truth, I can't see anything else.
Williams 6-0 2-0* DiatchenkoBREAK! A few more double faults suffered by Diatchenko now, as she loses the second game without winning a point. And the trainer is back now! I've got a feeling she'll retire.
1.27amGAME SET MATCH! Right on cue, Diatchenko, suffering with an ankle injury of some description, retires to postpone an inevitable whitewash!
1.28amSo, the six-time champ progresses. Was it ever in doubt? Nope. Utterly dominant. It's hard to know how much of the rout was contributed by Diatchenko's injury. Williams won't care. It wasn't even a training exercise. There seemed a gulf in class. Diatchenko only won FIVE points in the eight games!
1.33amRESULT! Speaking of retiring, world number 120 Illya Marchenko also moves into the second round after Gael Monfils - ranked 16th in the world - retired toward the end of the third set. The Frenchman won the opener 6-2, before Marchenko hit back 6-4 to level up. However, Monfils's condition then waned as he suffered a 5-0 third-set deficit, before calling it a day. We'll have both reports up shortly.
2.03amHere is Williams rep and the Monfils one is coming straight up. Incidentally, Nadal and Coric has begun. It's two games apiece in the fist set there.
2.30amSET! Has the real Rafael Nadal stood up? Well it's too early to know that, but what we do know is that he has moved into a one-set lead over Borna Coric after winning the opener 6-3!
2.38amAs promised, here is how Gael Monfils had to retire from his first-round clash with Illya Marchenko. Big shame. A lot of people - myself included - were looking forward to seeing the entertaining Frenchman. Oh well.
3.01amSET! Rafael Nadal is in great shape so far against Croatian rookie Borna Coric - playing some impressive tennis, looking in complete control - and he's just taken the second set 6-2!
3.48amSET! Could the comeback be on for Coric? Nadal had been looking comfortable, but an early break helped the 18-year-old to take the third set 6-4. Game on!
4.25amBREAK! Coric and Nadal were going toe-to-toe in the fourth set, but Nadal has just produced what could be a crucial break point to edge towards victory against the young Croatian.
4.40amGAME SET MATCH! It's all over at Flushing Meadows, with two-time champion Rafael Nadal keeping his composure to claim a first round win over youngster Borna Coric, taking the fourth and final set 6-4. Coric looked impressive throughout, but the experienced Spaniard had too much for his rookie opponent in the end. Match report to follow...
4.52amAs promised, here is the full report on how world number eight Rafael Nadal defeated youngster Borna Coric in his opening round fixture at Flushing Meadows this morning.
4.55amAnd that concludes Sports Mole's coverage of the first day at the US Open, thanks for your company over the last 13 hours! We'll be back with all the action from Day Two at Flushing Meadows later today - goodnight!