12.49pmThere's no chance of a slow start this year; day one is packed full of big name. On Centre Roger Federer begins his defence against Victor Hanescu. That match is being covered by Pascal Lemesre - here. Also today Andy Murray, Jo-Wilfried Tsonga and Rafael Nadal play.
12.52pmSo Serena Williams is of course the heavy favourite for the women's title this year, but she will have some tough opponents to get through, including Azarenka. The Belarusian has never been in the final here, but reached the last four in both of the last two years.
12.55pmShe does have two slams to her name - the Australian Open, which she has won on the last two occasions. Much more a hard court specialist, she has also made the final of the US Open. But what of her opponent?..
12.57pmIn early exit news - Elena Baltacha becomes the first British casualty at SW19 this year. She has just been beaten by Italian Flavia Pennetta 4-6 1-6.
12.59pmBack to this match and a quick look at our Portuguese competitor. The 20-year-old has yet to claim a WTA title, but does have three ITF ones to her name. In terms of slams, she has only qualified for any this year. She reached the second round at Melbourne earlier in the year, but lost her opener at the French. This will be her first appearance at Wimbledon.
1.03pmSo there's really not a great deal of research that the Belarusian could have done for this one. Which I suspect means Koehler's best chance of causing an upset or even a fright will come early on.
1.06pmHere come the players. Azarenka, of course, walks out to her 'banging tunes'. I'm sure we'll find out at some point during the day what exactly she was listening to - rather than hearing about the important things, such as the match.
1.09pmShe's not nearly as tall as Azarenka, but Koehler is certainly built for power. She surely can't be expecting to get through today, but even if she takes only a few games she should learn from the experience. I'm focusing on her age, but she is only three years younger than Azarenka. And of course many on the WTA tour have had Slam wins by her age.
1.11pmWith a minute of the warm-ups left, we're nearly set for the first No.1 Court action of the year. As ever, the grass looks immaculate and for now the weather looks as though it will hold up. It's cloudy, but it's not expected to rain. Plans are afoot to cover this court as well as Centre, but that won't be for a couple to a few years yet.
1.13pmHere we go then, let's get underway. Azarenka will serve first...
1.14pmAn early double fault from Azarenka. Not a great start with the ball for her - 15-15.
1.15pmMake that two... 15-30. She's wasted a review as well with a ball clearly wide.
1.15pmWell I never. The Portuguese has been buoyed and a forehand winner from the lefty brings her two break points...
Koehler *0-1 AzarenkaKoehler is really close to an early break as a powerful return goes just an inch or two wide. Azarenka responds to her early serving problems to finally find the box and see out her first game. An exciting start to the match, if only for the errors.
Koehler 0-2* AzarenkaBREAK! Here's out first chance to see the serve of Koehler then. It's nothing too dangerous, but she passes Azarenka nicely after bringing her to the net with a low bouncing forehand. Then it's just too good form Azarenka - the power and deception of her shots eventually telling for two break points. Better from the Portuguese, who forces the error from her opponent following a spinning first serve, but she goes wide on the next point and is broken early.
1.22pmReally good point there - but you have to say Koehler is just too defensive. She's in control, but after Azarenka reaches a couple of attempted winners she starts to slice her returns and the Belarusian takes the point that she really shouldn't have.
Koehler *0-3 AzarenkaA much more convincing service game from Azarenka, and this is not looking good for Koehler at the moment. She must get a game soon.
1.26pmThat's better from the Portuguese. Again Azarenka advances, and again Koehler gets the better of her. This time the second seed got a touch on the pass, but it was hit too well.
1.28pmTwo rallies and both end with the point going to Azarenka. We're at deuce because of her dominance from the baseline here.
Koehler 0-4* AzarenkaBREAK! Koelher reponds to deuce with a big serve and the finish, but we're back to 40-40 as Azarenka has the whole court in which to aim the winner. Koehler doesn't quite have the confidence to go for the corners, but when she does she finds the tramlines for break point. An unstoppable return brings up another break, and this is only going one way.
Koehler *1-4 AzarenkaBREAK! She must serve better when she gets further into the tournament. She opens her next game with her fourth double fault, but she masks this slight issue with some bullying shots from deep. There's our first slip of the tournament on No.1 Court - but Koehler is fine. Azarenka, however, makes it double fault five for deuce. Much, much better from the youngster, who gets break point after finally winning a rally. She's in on second serve and another pass with Azarenka advancing gets her one of the breaks back!
Koehler 1-5* AzarenkaBREAK! A timely first ace for Koehler moves her up 30-15 in an important service game. It's followed by her second for 40-30. She looks to finally be finding her feet over the past couple of games, but the second ace is followed up by a second double fault to bring deuce. All of a sudden she finds the net and Azarenka has a break point, but it's well saved with some aggressive hitting. On Koehler's advantage, the world No.2 swats a backhand return winner; sublime shot. Koehler skews a forehand long, and follows it with another - Azarenka breaks right back and will now serve for the set.
Koehler 1-6 *0-0 AzarenkaSET! Much, much better serving from Azarenka. Two aces bring up two set points and she finishes it with a quite brilliant backhand winner right on the line. Its a little flattering, perhaps, but Azarenka is racing into the second round.
1.48pmFederer also looks to be wasting no time over on Centre. He's two breaks to the good in the second set and holds a 3-0 lead.
Koehler 1-6 0-1* AzarenkaBREAK! Koehler is doing all the running here. She has to, as her opponent is sending her right to left and back again. Koehler responds at 0-30 with a fantastic swinging serve down the middle that cannot be returned. But she's back to the running and in a rally there's only one likely winner. That brings up two break points. Azarenka goes long with the first and the second is saved emphatically with a one-two forehand winner. At deuce, Azarenka moves to smack a winner, but shifts to drop it just over the net - lovely. Koehler nets on the third break point, and it's an early Azarenka advantage in the second.
1.56pmFantastic from the Portuguese. Azarenka is dominating a rally before Koehler finds the line with a forehand and moves in for the kill. It's 15-15.
1.58pmAnother really good rally, and again it goes the way of the Belarusian with Koehler just running out of patience and going long.
1.59pmFrom 40-30 down, Koehler has a break point as Azarenka smacks a simple forehand wide.
2pmOh my, that was a horrible noise... Azarenka slips trying to turn and is in tears in a heap. That could be the end of Azarenka, she seems in a lot of pain.
2.02pmOn quite a few occasions you see players wailing as they slip - as much in surprise as pain. It's hard to tell which it is here, but she looks in a little less discomfort. Here finally comes the trainer (where on earth are they stationed?!) and Koehler is across as well, concerned for her opponent.
2.07pmAzarenka is on her feet, which is great to see. When she first slipped, her tears made it sound like that was it for her. She's walking gingerly over to her bench, and she may well be able to carry on.
2.08pmThe medical timeout has begun. So three minutes begin from here. All that was the evaluation phase - the trainer now has 180 seconds to make it all better. I'd be surprised if she didn't carry on now.
2.12pmApplause from the crowd as Azarenka comes back out to serve. Her leg is heavily strapped and this will be an interesting few games. She starts with a double fault...
2.13pmFollowed by another... Three into the net and one long. Now it's advantage Koehler.
Koehler 1-6 *1-1 AzarenkaBREAK! Better from Azarenka, who saves break point with a big serve followed by a volley across court. However, Koehler gets the advantage and wins with Azarenka going wide. She's still far from fluid.
2.16pmWhat does a player do in this situation? Does Koehler take advantage by hammering the corners? At the moment she's being almost considerate and hitting the ball down the middle. Either way, Azarenka isn't hitting accurately so it doesn't really matter.
2.20pmBelieve it or not, it's over already on Centre. Federer has smashed Hanescu 6-3 6-2 6-0 and he just got better and better through the match. It took just over an hour! Incredible stuff.
Koehler 1-6 1-2* AzarenkaBREAK! It's a gruelling game with several deuces and Azarenka is really struggling on her forehand side when she has to plant her weight. I'm not quite sure how, but she's broken back without even being able to run. It's hard on Koehler, who certainly seemed to be a little generous with her shots.
Koehler 1-6 *1-3 AzarenkaBoth players smack the ball right down the middle; it's Azarenka who veers off course into the corner, but Koehler who takes the point streakily hitting the top of the net. However Azarenka, now moving much better, holds comfortably to 15 - probably her best service game so far.
Koehler 1-6 2-3* AzarenkaKoehler is down this time, but she's up pretty quickly. She was moving backwards and not side-to-side, which made hers much easier to control. It's a really good game with both women showing power and poise, but it's the Portuguese who holds importantly.
Koehler 1-6 *2-4 AzarenkaSuddenly Azarenka's serve is impressive. When she's finding the target it really gives Koehler little chance. A second successive hold to 15 moves her just two games away from the second round.
2.35pmIt's Azarenka's turn to get lucky - finding the very top of the net with a forehand and it drops just over for 0-30.
Koehler 1-6 2-5* AzarenkaBREAK! Fantastic winner to take the break for Azarenka. She was made to work and run in that came, but when she got the chance she made no mistake - firing a forehand into the corner to move one service game away.
2.42pmBad time for a double fault, so close to the end. It brings it to 30-30 and a wide forehand across court gives Koehler the chance to break - it was about two millimetres out!
2.45pmThat was an awful lot tougher than she had hoped - mainly due to the injury scare - but there was enough in that performance to encourage her. Koehler gave a good account of herself, but was just not good enough in any area in truth.
2.47pmShe'll have a couple of days to recover, but for now she will be glad that she was able to complete the match. Her opponent in the next round is Italy's Flavia Pennetta, who beat Elena Baltacha earlier.
2.49pmThanks for joining me today. Please do stick around for all the reaction, results and upcoming commentaries. Head over to our Wimbledon page here for all you could need. Goodbye.