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Novak Djokovic beats Alexandre Muller 6-1 6-7 (7-9) 6-2 6-2
Coco Gauff stunned in straight sets by Ukraine's Dayana Yastremska
Britain's Jack Draper through to second round as Sebastian Baez retires with injury
GB's Dan Evans beats compatriot Jay Clarke while Jack Pinnington Jones also progresses
But Heather Watson, Johannus Monday, George Loffhagen, Jodie Burrage & Francesca Jones all exit
Jannik Sinner, Barbora Krejcikova and Iga Swiatek win but third seeds Jessica Pegula and Alexander Zverev out
*Muller 1-6 7-6 (9-7) 2-6 0-0 Djokovic
Harry Poole
BBC Sport at Wimbledon
What a rollercoaster this is proving to be.
Only five games ago, Novak Djokovic appeared to be in trouble. Instead, he appears to have rediscovered his form and wins five games in a row to take back control of this match.
This must all be rather baffling for Alexandre Muller. The crowd absolutely love it, though.
Muller 1-6 7-6 (9-7) 2-6 Djokovic
Novak Djokovic barely reacts as he takes the third set to regain the lead.
He looked back to his best in the second half of that set, playing more aggressively and forcing the issue.
Muller 1-6 7-6 (9-7) 2-5 Djokovic*
Andrew Castle
BBC Sport tennis commentator on BBC TV
That is superb from Novak Djokovic! From medical timeout to 5-2 and two breaks in the blink of an eye.
It's almost like he needed a crisis to get some adrenaline going. The sheer fright of losing can sometimes jolt you into action.
Muller 1-6 7-6 (9-7) 2-5 Djokovic
Brilliant from Novak Djokovic.
After missing his first break point, he takes his second by sending a scintillating backhand down the line which Alexandre Muller can't return.
The Serb will serve out for the third set.
*Muller 1-6 7-6 (9-7) 2-4 Djokovic
Maybe that time-out has helped Novak Djokovic?
He made light work of his service game there, with a couple of serve & volleys to put the pressure back on Alexandre Muller.
Harry Poole
BBC Sport at Wimbledon
The doctors are being kept busy on Centre Court.
There has been an obvious shift in Novak Djokovic's body language in this set. He looks sluggish moving between points and there's clearly been a dip in his energy.
The Serb is given another tablet to take while, on the other side of the umpire's chair, Alexandre Muller has a medical timeout to receive treatment on his right calf.
Muller 1-6 7-6 (9-7) 2-3 Djokovic*
If Novak Djokovic is struggling, he didn't show much sign of it there.
The Serb gets a crucial break - his first since the first set - after Alexandre Muller double faults.
Kim Clijsters
Four-time Grand Slam champion on BBC Radio 5 Live and BBC Sounds
Image source, Getty ImagesIn between the points, Djokovic looks very down and physically unwell but once the point gets going we still see him sliding and doing the Novak things we see.
The crowd are starting to feel like they need to get behind him to push him and give him positive energy - at the moment he is not able to do that himself.
Harry Poole
BBC Sport at Wimbledon
It looks as though Novak Djokovic just had something added to his drink there, rather than any treatment on a physical problem. You'd guess maybe something like electrolytes for energy, given the temperatures today, but it's impossible to tell for sure from here.
*Muller 1-6 7-6 (9-7) 2-2 Djokovic
That was precisely the type of service game that Novak Djokovic would have wanted after that medical time-out, as the Serb easily holds to 15.
Muller 1-6 7-6 (9-7) 2-1 Djokovic*
Novak Djokovic didn't look best pleased during that medical time-out but he's playing on - for now - at least.
Muller 1-6 7-6 (9-7) 2-1 Djokovic*
Andrew Castle
BBC Sport tennis commentator on BBC TV
Novak Djokovic really doesn't look in the mood to grind out 22-shot rallies at the moment.
Whatever is wrong, it is certainly affecting his game at the moment.
Everything feels worse when you are that disappointed though, after all of those chances in the second set.
Muller 1-6 7-6 (9-7) 2-1 Djokovic
Alexandre Muller holds and Novak Djokovic instantly makes a rush for his chair.
He appeared to request for the doctor before the last game and his body language hasn't been right since the start of the third set.
*Muller 1-6 7-6 (9-7) 1-1 Djokovic
Point of the match so far.
Alexandre Muller thinks he's won the point when he sends a tame overhead back to an empty court but Novak Djokovic returns out of nowhere to clip a ball back, before sending a forehand winner across court.
*Muller 1-6 7-6 (9-7) 1-1 Djokovic
Now it's Novak Djokovic's turn to struggle on serve.
The world number six is frustrated with himself as he misses two opportunities to put Alexandre Muller away.
His body language is certainly different than it was midway through that second set.
He eventually gets over the line as Muller sends a forehand into the net.
Muller 1-6 7-6 (9-7) 1-0 Djokovic*
Tim Henman
Former British number one on BBC One
A brilliant strike on the forehand but just watching the body language of Novak Djokovic, it looks a little despondent after that second set.
Yastremska 7-6 (7-3) 6-1 Gauff
Image source, Getty ImagesDayana Yastremska, speaking on court after her victory over French Open champion Coco Gauff: "This court brings a lot of nice memories. I played the junior finals on this court so it gave me a lot of emotions.
"I think it was a great match today, I was really on fire! Playing against Coco is something special, we have played four times now and it is 3-1 to her. She is a great player and person.
"These courts are made for the greatest players and I am very grateful to be on this court. Thank you so much for the support.
"My preparation before the grass season didn't go very well - I got sick at Roland Garros and I only trained two days on grass. It was pretty unexpected but it has been a great season for me. I love playing on grass, I feel like this season we are friends!
"I hope the road will continue, and it is a pleasure to be here."
Muller 1-6 7-6 (9-7) 1-0 Djokovic*
Tim Henman
Former British number one on BBC One
Another good hold for Alexandre Muller after battling through that second set.
He will want to make sure he doesn't have any dips in intensity and put out some more strong service games.
The next step will be to try to put some pressure on Novak Djokovic's serve because he is yet to have a break point.
Muller 1-6 7-6 (9-7) 1-0 Djokovic*
Alexandre Muller gets the early hold. That's about as comfortable a service game as he's had so far in this match.
His confidence is clearly up after that tie-break victory.
Tracy Austin
Two-time Grand Slam champion on BBC TV
Image source, Getty ImagesWhat a performance from Yastremska, the performance of her life. She came out with so many weapons and so much power, she was able to contain it.
She served smart, big and threw in some off-paced serves as well. It was a very well planned match.
Gauff never really felt comfortable on the grass, she didn't have a lot of lead-up matches coming into Wimbledon. She was so gracious at the handshake.
