Marcus Rashford got the visitors off to a perfect start with the opening goal after less than two minutes, and he added a second midway through the half before Marouane Fellaini sent United into the break with a three-goal lead.
Find out how all of the action unfolded courtesy of Sports Mole's minute-by-minute updates below.
2amGood morning! Rise and shine and thank you very much for joining Sports Mole for this pre-season friendly between Los Angeles Galaxy and Manchester United at the Stubhub Center! For all of you early risers (or late finishers), this will be United's first match of pre-season and hopefully they will put on enough of a show to keep us all awake. Before we go any further, though, let's first take a look at the team news...
2.02amLA GALAXY SUBS: Rowe, Van Anholt, Romney, Van Damme, Cole, João Pedro, Jones, Alessandrini, Giovani, Boateng, McBean
2.04amMAN UTD STARTING XI: De Gea; Valencia, Jones, Smalling, Blind; Carrick, Herrera, Fellaini; Lingard, Mata Rashford
2.06amWhat can we make of those two teams, then? Well, unsurprisingly LA Galaxy have left a number of their key players on the bench today as they take the opportunity to rest a few of the bigger names in the middle of the season. The most recognisable figure in their squad for fans of English football is Ashley Cole, but he has to make do with a place on the bench from the start tonight.
2.08amFormer Tottenham Hotspur forward Giovani dos Santos joins Cole amongst the substitutes having only recent returned to the side following two months away with the Mexican team during their participation in friendlies, qualifiers and the Confederations Cups. He has scored six goals in 12 MLS appearances this season, though, so will be a threat to the United defence should he be given a runout later tonight.
2.10amAnother one of the Galaxy's key players is Romain Alessandrini, who also starts tonight on the bench. He has directly contributed to 14 goals from the MLS matches he has played since joining LA Galaxy, and the team certainly missed him during their last outing when they were thrashed 6-2 by Real Salt Lake.
2.12amIn all, LA Galaxy have made seven changes from the side that was beaten 3-2 by San Jose Earthquakes last time out, with Diallo, Garcia, Villarreal and Jamieson the only players to keep their places from that one. New captain Van Damme is amongst those to drop out of the starting XI alongside Rowe, Romney, Boateng and McBean, in addition to the high-profile trio I have already mentioned.
2.14amAs for Manchester United, fans will have to wait a little bit longer to see either Victor Lindelof or Romelu Lukaku in the shirt as both have been left out of the starting XI for this one. Jose Mourinho does plan to introduce a completely different team for the second half, though, so both players are likely to make their debuts then following their summer moves from Benfica and Everton respectively.
2.16amDavid de Gea will start in goal for United tonight but will be replaced at half time by Pereira, while Mourinho has already confirmed that Romero will get playing time against Real Salt Lake in the next match. The rumours linking De Gea with a move to Real Madrid refuse to go away, and they are likely to strengthen while the two clubs share training facilities in Los Angeles, but for now the Spaniard remains a United player.
2.18amSmalling and Jones have also been linked with moves away this summer, but they make up the starting central defensive pairing for United tonight. Valencia and Blind make up the defensive quartet, and in front of them Michael Carrick will wear the armband for the first time since being officially installed as the club's new captain following the departure of Wayne Rooney back to Everton.
2.20amIn all, the side shows just four changes from the one that started their last outing - the Europa League final victory over Ajax. Rashford again leads the line ahead of the likes of Martial and Lukaku, while Mata, Herrera and Fellaini are amongst those to retain their place from that side. There is no room for Paul Pogba from the start, though, as Jesse Lingard comes into the team.
2.22amIt is still a strong United side, though, and for many of these LA Galaxy players this will be a privilege to play against a team of United's calibre. It could come as a welcome relief from what has been a difficult league campaign to date too, although one thing Curt Onalfo will be keen to avoid is a thrashing which may only do more harm to the Galaxy's morale at the moment.
2.24amHaving said that, LA Galaxy were on the end of a 7-0 drubbing at the hands of United on the Red Devils' last visit in 2014 and they went on to win the MLS Cup that year - the third time they had lifted the trophy in a four-year spell. It remains their most recent title, though, and their dominance of the division certainly seems to be on the wane now having failed to even make it past the Western Conference semi-finals in the past two years.
2.26amThe Galaxy are in danger of missing out on the playoffs altogether this year, with the team currently sitting eighth in the Western Conference, two places and two points adrift of the top six. Curt Onalfo's side do have games in hand over many of the other teams in the league, but they are only four points off the bottom and a full 10 adrift of the leaders so there is still plenty of work for them to do over the remainder of the campaign.
2.28amGalaxy come into this match in particularly poor form having lost four of their last five games, including each of their last three. The only win from their last five outings came against lower-league Sacramento Republic in the US Open Cup - which they were subsequently eliminated from in the quarter-final stage against San Jose Earthquakes on Tuesday.
2.30amThis recent slump in form follows a nine-match unbeaten streak which saw Galaxy win five and draw four games, which makes things even more alarming for Onalfo. They are looking to avoid falling to a fourth consecutive defeat for the first time since May 2012, but they have a job on their hands having conceded nine goals in their past two games - including a 6-2 thrashing at the hands of Real Salt Lake.
2.32amThat Salt Lake match was LA Galaxy's most recent home outing, and it is their form at the Stubhub Center which has let them down more than anything else this season. Indeed, the Galaxy have the very worst home record in the entire MLS this season having picked up just six points from their nine games, also conceding a league-high 18 goals in front of their own fans.
2.34amInterestingly, LA Galaxy have the best away record in the MLS while also having the worst home record, which suggests that they can be a very hit and miss team. They are winless in their last six MLS home games and have only won one of nine all season, while in friendlies they have only won one of eight in front of their own fans - the most recent of which was that 7-0 defeat at the hands of United three years ago.
2.36amThat 2014 result got Louis van Gaal's reign off to a flying start at United, but it also serves as a warning that even the most impressive of performances tonight does not necessarily mean a bright season ahead of the Red Devils. The 2016-17 campaign was a strange one in many ways for the club, with the fans unhappy for much of the season but United ending it with three trophies to their name, including the Community Shield.
2.38amUltimately, Jose Mourinho's debut campaign at Old Trafford will go down as a successful one as he lifted the League Cup and the Europa League, achieving Champions League qualification through the latter. However, the success of that season rested on the result of that Europa League final and United will not want to leave it so finely balanced this time around. Improvement in the Premier League will be the first thing that is demanded, with United finishing in a lowly sixth place last season.
2.40amDraws were United's main issue as they finished seven points adrift of the top four and 24 behind champions Chelsea last season, with the Red Devils sharing the spoils on a league-high 15 occasions. United were only actually beaten five times - only Spurs lost fewer games - but those 15 draws accounted for 30 dropped points which could have had United up there challenging for the title had they turned the majority of them into wins.
2.42amThe ability to turn those draws into wins will be one of the priorities for Mourinho during the upcoming campaign, which officially gets underway today with their opening pre-season match. Today marks the start of a run of five games in 11 days during United's pre-season tour of the United States, with a clash against Real Salt Lake to follow on Monday. During their time in America United will also take part in the International Champions Cup, where they will face Manchester City, Real Madrid and Barcelona over the coming week or so.
2.44amAfter that, the Red Devils will travel back to Europe for more friendlies against Valerenga and Sampdoria before the real business gets underway with the European Super Cup against Real Madrid on August 8. United have been in Los Angeles for a week already in the build-up to this match, so that would complete a month-long pre-season campaign which should get them adequately prepared for the start of the new Premier League season.
2.46amUnited have been handed a relatively kind start to the new league season on paper, opening their campaign at home to West Ham United and not facing another member of the top six until they take on Liverpool in mid-October. Before then, United will play the Hammers, Swansea, Leicester, Stoke, Everton, Southampton and Crystal Palace in their first seven games, so fans will be hopeful of making a strong start to the campaign.
2.48amBefore all of that, though, United will be hoping that this pre-season campaign is significantly more successful than last summer's, when they faced an energy-sapping trip to Beijing only to see their friendly against Manchester City rained off. There is very little chance of the same happening in the States, though, and with a relatively new complexion to the United squad following the departures of Rooney and Ibrahimovic, there is an air of optimism amongst supporters that this will be a much better campaign on the whole.
2.50amPREDICTION: Right, we're 10 minutes away from kickoff at the Stubhub Center, which means that it is time for a prediction! It is always difficult to make a reasoned guess in pre-season, with United focusing more on fitness whereas LA Galaxy should be at full fitness as they are in the middle of their season. Different teams in both halves make it even tougher to call, but the quality at United's disposal should see them through. We're going for a 3-1 United win.
2.52amAs previously mentioned, United kicked off their 2014 summer tour of the United States with another match against LA Galaxy, and it couldn't have gone much better on that occasion as they ran out 7-0 winners in Louis van Gaal's first game in charge of the club. Welbeck opened the scoring on that occasion before Rooney, James and Young all helped themselves to braces to complete the rout.
2.54amUnited may be hard-pressed to repeat that achievement here today, but first and foremost they will treat this as an opportunity to get back up towards full match fitness. The United fans will probably be most excited to see Lukaku make his debut for the club following his £75m move, which could rise as high as a world-record £90m fee. It is a huge amount of money for a player Mourinho previously deemed not good enough during his time at Chelsea, but it is hard to argue with Lukaku's goalscoring record at just 24 years old.
2.56amUnited are expected to bring more players in between now and transfer deadline day, with the main talk at the moment regarding a defensive midfielder. Chelsea's Nemanja Matic appears to be at the top of Mourinho's wish list, although Roma's Radja Nainggolan has also been touted as a possible target. These string of matches in the American tour should help Mourinho pinpoint exactly what else he needs before the start of the new season.
2.58amRight, we're almost ready to go here! The players are out and we're just a couple of minutes away from kickoff at the Stubhub Center as United prepare to get their 2017-18 campaign underway.
3amMLS games are notorious for going past their scheduled kickoff time, and their pre-season friendlies are no different - we have some formalities to go through before we will actually get underway here.
3.02amThe American national anthem is sung prior to kickoff, with fireworks in the background as both sets of players line up. How very American.
1 minKICKOFF: Here we (finally) go then! LA Galaxy get us underway for United's opening pre-season of 2017-18.
2 minGOAL! LA Galaxy 0-1 Manchester United (Marcus Rashford)
2 minWhat a start to the season for United! Less than two minutes into their opening pre-season game and they already have the lead! Smith is caught in possession deep inside his own half, with Lingard getting a foot in and poking the ball to Rashford. Suddenly the striker finds himself with only the keeper to beat, and he makes no mistake by tucking his finish into the bottom corner with aplomb.
4 minThat is a nightmare start for this rather makeshift LA Galaxy side, who have started very nervously here. United are applying the pressure at the right time when they don't have the ball and already they have threatened to break in behind the defence on a couple of occasions. This could be a long game for the hosts.
6 minRashford in particular is looking sharp in these opening minutes, with his pace in behind looking to be the weapon of choice for United so far. His finish was very precise for the goal too - no signs of rust from the England international.
8 minGalaxy make their first promising break forward as Blind fails to cut out a long diagonal ball over to the right flank. It is given back to Jamieson, who tries to poke a ball through, but his pass is intercepted and United clear the danger.
10 minAlmost a chance for Galaxy to get back into this one, and again it comes via a Blind error. This time the Dutchman misses his kick in the area and the ball drops to Jamieson, but he can't get a shot away from the edge of the box.
12 minSHOT! Rashford looks to double his individual tally as he ducks inside from the right flank before trying to pick out the bottom corner with the outside of his boot, but he fires it wide of the target.
13 minGalaxy have the chance to counter, winning the ball back and immediately breaking in a two-on-two situation. Lassiter leads the charge, but he tries to go alone past Jones who defends it well and is able to knock it behind for a corner.
15 minSAVE! Almost a beauty from Mata as he digs out a sublime effort born from a lack of other options. Lingard threads the pass through to the Spaniard on the edge of the box, who looks around for support before deciding instead to go alone with an audacious lob. Kempin is worried in the Galaxy goal, but he scrambles back and manages to claw it away.
17 minLA Galaxy have certainly settled into the game more as this half has progressed, and they have done well to avoid any further damage after that early goal, but it is United who remain in control of the contest as things stand. Mourinho's side continue to look dangerous almost every time they come forward.
19 minSmart play from Rashford as he spins away from his man just inside the LA Galaxy half, only to be hauled to the ground.
20 minGOAL! LA Galaxy 0-2 Manchester United (Marcus Rashford)
20 minUnited have their second, and it is Marcus Rashford who doubles his personal tally for the game. Again it comes from United winning the ball back inside the LA Galaxy half, with Herrera this time nipping in. He gives the ball to Mata, who in turn plays a pass through for Rashford. The England man again has only the keeper to beat, and he cooly rolls it into the bottom corner to leave himself on a hat-trick after just 20 minutes.
22 minIt has been far too easy for Rashford to get those two goals, and Romelu Lukaku will be licking his lips at the prospect of getting on now. It looks like there will be goals out there for the new signing.
24 minLA Galaxy are struggling to get out of their own half right now. They have not tested De Gea at all so far in this first half and it looks as though it could already be damage limitation mode for the hosts.
26 minGOAL! LA Galaxy 0-3 Manchester United (Marouane Fellaini)
26 minUnited have their third of the game and this is already threatening to be another rout against LA Galaxy. Lingard reaches the byline down the left channel before cutting back and picking out the pass for Fellaini, who strokes his left-footed finish home from the edge of the area.
28 minCLOSE! United are pushing for a fourth now and Lingard collects the ball on the corner of the area before cutting inside onto his right foot and looking to pick out the top corner. His effort is decent enough, but it lands on the roof of the net.
30 minWe're half an hour into this pre-season friendly now and it is hard to imagine how it could have gone much better for Jose Mourinho's side. They are in complete control here and it would be a big surprise if they didn't add to their lead before half time the way this match is going.
32 minOne of the biggest cheers of the night so far greets a picture of David Beckham on the big screen - a legend for both of these clubs, of course.
34 minSHOT! Good spell of possession again for United as they knock the ball around at their own pace inside the Galaxy half. The ball eventually ends up at the feet of Rashford, who fires a shot over the bar from the edge of the area. That would have been some team goal.
36 minAshley Cole is amongst the substitutes warming up for LA Galaxy at the moment, which suggests that the former Arsenal and Chelsea full-back could be coming on in the second half.
38 minUnited break forward again as Valencia reaches the byline down the right channel before standing a cross up to the back post for Fellaini, who attempts to nod it back into a dangerous area. It is read well by the defence, though, and they clear the danger.
40 minCHANCE! These United players out there want a fourth goal before the change of team at half time! Rashford drives forward from the left flank before laying the ball off for Mata, who takes a touch before firing an effort wide of the near post.
42 minDISALLOWED GOAL! United do have the ball in the back of the net for a fourth time, but the linesman's flag is up for offside. LA Galaxy fail to clear their lines from a free kick and the ball drops to the feet of Carrick, whose low snap shot is saved by the keeper. The ball rebounds out to Smalling who tucks away the finish, but he does so from an offside position.
43 minCHANCE! Huge chance for Rashford to wrap up a first-half hat-trick! A ball over the defence finds the youngster clean through on goal having beaten the offside trap, but he seems to have too much time if anything and his low strike is well saved by Kempin.
4amThe first half comes to an end at the Stubhub Center, and it was all very comfortable for United. They never needed to get out of second gear on their way to a 3-0 lead at the halfway stage of their opening pre-season friendly, and in truth it could be even more emphatic for the Red Devils at the break.
4.02amUnited got their pre-season campaign off to a perfect start with a goal after just two minutes through Marcus Rashford, who latched on to Lingard's pass before sliding his finish into the bottom corner. United won the ball back inside the LA Galaxy half, which has been a theme of the game so far, and Rashford was clinical in applying the finish.
4.04amRashford and United both had a second after 20 minutes, and it was a similar goal in may respects as the Red Devils once again won possession in an advanced position. This time it was Herrera who stole the ball in a dangerous position before poking it to Juan Mata, who in turn played a through-ball to Rashford. Again the youngster was cool in front of goal, rolling his finish into the bottom corner.
4.06amThe third goal came just six minutes after the second as Marouane Fellaini got in on the act, placing a left-footed finish home from the edge of the penalty area after good work from Lingard down the left channel. The wing-back reached the byline before cutting back and teeing Fellaini up, and the Belgian made no mistake with his finish.
4.08amIt will be all change for United at the break, and here is their second-half XI - including debuts for Lukaku and Lindelof.
46 minKICKOFF: Lukaku gets the second half underway with his first touch as a Manchester United player.
48 minUnited have quickly resumed control of possession in this second half, and it is a particular strong and powerful side out there now with the likes of Lukaku and Pogba on the field.
49 minCHANCE! Huge chance for Lukaku to open his United account nice and early as new goalkeeper Rowe gives the ball away to Pogba, who gives it to Lukaku to try to gift him his first goal for the club. Rowe more than atones for his error, though, by making a brilliant stop to deny the new striker.
51 minLukaku acts as provider this time, holding off two LA Galaxy midfielders from the resulting corner before playing the ball back for Mkhitaryan, but the Armenian completely mis-hits his shot and it goes well wide.
52 minChance for United to break as Martial gives the ball to Lukaku, who in turn threads it through for Mkhitaryan. The winger tries to cut inside onto his left foot, and Ashley Cole is back there and makes a good challenge.
53 minSHOT! Lukaku gives a glimpse of his power by shrugging off the challenge of Ashley Cole on his way forward before getting a shot away, but he fires it comfortably wide of the target.
55 minThe Galaxy win a corner and it produces their first real sight of goal of the entire match. Pereira comes off his line but gets nowhere near the ball, and it takes a hasty clearance from Lindelof to hack the ball away.
57 minHe may have moved all the way to Los Angeles, but Ashley Cole cannot get away from the boo boys! He is being jeered by the United fans inside the Stubhub Center every time he touches the ball.
58 minI think this counts as LA Galaxy's first shot of the match, although it may be generous to call this a shot. It comes from Ashley Cole, much to the fans' delight, as he blazes an effort a long way high and wide of the target.
59 minCLOSE! United respond with a long-range effort of their own, but this one is a lot better. Martial is afforded space on his right foot from around 30 yards out and he drills a powerful strike towards goal which zips narrowly over the crossbar.
61 minLA GALAXY SUBS: LA Galaxy make two changes as Alessandrini and Jones replace Lassiter and Garcia - the two players who had stayed on at half time.
62 minCHANCE! Another chance for United to add to their tally, but once again Rowe denies the visitors. Darmian bursts forward down the left flank and plays the ball through for Martial, only for the Frenchman to see his effort kept out by the keeper.
64 minCHANCE! Mkhitaryan bursts into life with a rampaging run down the middle of the pitch, flying forward from midfield before laying it off to Lukaku. Lukaku returns the favour by finding Mkhitaryan again, but the Armenian sees his shot deflected wide.
65 minAnother shooting chance for United as the ball breaks to Darmian outside the box, but his attempted effort is deflected behind for another corner.
66 minCHANCE! Lukaku has missed a sitter to score on his debut, and now Lindelof has done so too. The ball drops to the defender inside the box from the resulting corner but he gets underneath his shot and blazes it over the bar with the goal gaping.
67 minGOAL! LA Galaxy 0-4 Manchester United (Henrikh Mkhitaryan)
67 minManchester United have their fourth, and the first of the second half, as Mkhitaryan tucks his finish past Rowe. Martial played the winger through and he sent the keeper the wrong way from the edge of the penalty area with a cool finish.
69 minLA Galaxy have certainly put up more of a fight in this second half with what is closer to their first-choice side, but United remain in control and in truth the Red Devils should have opened the scoring in this second half earlier than they have done.
70 minLindelof bursts forward from defence, ending up in the centre-forward position, but Fosu-Mensah wastes the opportunity by firing over the bar from the edge of the area when he should have looked for a teammate.
72 minGOAL! LA Galaxy 0-5 Manchester United (Anthony Martial)
72 minIt is officially a rout. United add a fifth goal as Pogba pings a brilliant ball down the right for Fosu-Mensah to chase. The wing-back gets to the ball before it runs behind for a goal kick and pulls it back for Martial, who applies a simple first-time finish. A five-star show from United in pre-season.
74 minThe only thing missing from this United performance at the moment is a Lukaku goal. I said in the build-up that United would struggle to repeat their 7-0 win from three years ago, but it could easily be more than that here.
76 minLess than 15 minutes remain in this opening pre-season friendly for United, and it is so far so good for Mourinho's side. He will be very happy with what he has seen so far.
78 minSHOT! Good play from Martial as he dips into shooting space before curling an effort towards goal which Rowe does well to get down and save.
79 minGOAL! LA Galaxy 1-5 Manchester United (Giovani dos Santos)
79 minThe hosts get a consolation goal with by far their best piece of football of the match. Dos Santos gives the ball to Alessandrini, who in turn plays it back to the former Spurs man inside the area. Dos Santos's first touch takes him past his marker and he then applies a confident finish into the bottom far corner to get the hosts on the scoreboard.
81 minThe ticker tape was released after that goal - a big celebration for a team that is 5-1 down!
82 minCHANCE! Almost a second for the Galaxy, who are suddenly looking dangerous when coming forward! Boateng does really well to keep the ball in and drive into the box before laying it off for Cole, who stands a cross up into the middle. Alessandrini gets his head to the ball, but Pereira makes the save from point-blank range.
84 minCHANCE! Another chance for United to add to their tally as Martial tries to curl it into the bottom corner, but he puts it a couple of yards wide when he should have done better.
86 minMAN UTD SUB: Late change for the visitors as Demetri Mitchell replaces Fosu-Mensah.
88 minGOAL! LA Galaxy 2-5 Manchester United (Giovani dos Santos)
88 minCue the ticker tape once more - LA Galaxy have scored a second! Romney gets his head to a corner, but it is Dos Santos who gets the final touch - albeit rather unwittingly. The ball just bounced off his thigh and crept into the corner past Pereira.
5.08amA good job well done for United in their opening pre-season outing, then, as they cruise to a comfortable 5-2 win over LA Galaxy. Marcus Rashford got the Red Devils off to a perfect start with a goal after just two minutes, and he added a second before Marouane Fellaini sent the visitors into half tie with a three-goal lead. Further strikes from Henrikh Mkhitaryan and Anthony Martial after the interval saw United take a 5-0 lead before a late brace from Giovani dos Santos made things more respectable for the hosts.
5.10amRight, that is all we have time for this morning! Thank you very much for joining Sports Mole for today's match as United open their pre-season campaign with a victory that also saw Lukaku and Lindelof make their debuts for the club. I will leave you with our match report, but from me it is goodbye for now!