LIVE: Novak Djokovic and Felix Auger-Aliassime in first set of quarter-final on Centre Court
Seven-time champion Djokovic has treatment for left calf problem at 4-4
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Gauff overcame fourth seed Jessica Pegula to reach her first Wimbledon semi-final
Alexander Zverev beats Jiri Lehecka in four sets to reach quarter-finals in match suspended on Monday night
Alfie Hewett wins in first round of men's wheelchair singles but fellow Briton Gordon Reid knocked out
Experience Centre Court Interactive with SIGNALS - click into real-time data analysis, quizzes and fan interaction
Auger-Aliassime 6-6 (4-3) Djokovic*
Nick Mullins
Tennis commentator on BBC Two
One of the observations that we might make in the middle of all this is that Novak Djokovic seems to be moving alright.
If he is still in pain, it isn't quite as obvious as it was 20 minutes ago.
Emily Salley
BBC Sport at Wimbledon
Novak Djokovic is starting to get agitated. He keeps looking up to the sky and waving his arms about.
I'm not sure if it's the light that's bothering him or if he's still struggling with that injury.
*Auger-Aliassime 6-6 (3-3) Djokovic
Maybe not - a weak backhand from the Canadian.
Serve has dominated all the first set - but not in this tie-break.
Novak Djokovic, by the way, seems to be moving a lot freer now after that earlier calf worry.
*Auger-Aliassime 6-6 (3-2) Djokovic
Auger-Aliassime outlasts Djokovic in a lengthy rally to dispatch a backhand volley at the net and recover that mini-break.
Oh and a stunning return turns the breaker right on its head! It's now the Canadian with the advantage after two points on the spin.
*Auger-Aliassime 6-6 (3-2) Djokovic
Tim Henman
Former British number one on BBC Two
Novak Djokovic didn't get the luck that time with the net cord.
His shot gave Felix Auger-Aliassime the time to hit that forehand, move forward and knock off a nice backhand volley.
Auger-Aliassime 6-6 (1-2) Djokovic*
Is this where the nerves will hit?
Felix Auger-Aliassime sends a backhand well long to hand Novak Djokovic an early mini-break in the breaker.
Auger-Aliassime 6-6 Djokovic*
When the Auger-Aliassime first serve hits, it's almost unreturnable.
That 12th game was a bit hit and miss from the Canadian but he does enough to hold to 30 - aided by some big serves - to take us into a first-set tie-break.
Image source, PA Media*Auger-Aliassime 5-6 Djokovic
Todd Woodbridge
Former Wimbledon doubles champion on BBC Two
This really is a tough period for Felix Auger-Aliassime because he has to stay so concentrated on his own end of the court and on his own game. He cannot afford to get drawn into Novak Djokovic's issues, such as wondering whether he is alright or whether he will carry on.
It is a hard thing to do.
*Auger-Aliassime 5-6 Djokovic
Nick Mullins
Tennis commentator on BBC Two
These are worrying moments if you are the son, the wife or a fan of Novak Djokovic - but he holds on in this set!
*Auger-Aliassime 5-6 Djokovic
Fabulous backhand winner down the line from Auger-Aliassime to elicit a break point - but Novak Djokovic replies with an ace bang down the middle.
And a great serve out wide puts the Serb back ahead in this service game. Another ace follows!
What a hold that is.
Image source, PA MediaAuger-Aliassime 5-5 Djokovic
There's a grimace with almost every Djokovic serve at the moment.
And the odd limp afterwards.
You suspect more treatment may be needed once this first set is over.
Felix Auger-Aliassime is sniffing blood here a bit, some big hits forcing Djokovic to move when he doesn't want to. Deuce.
Emily Salley
BBC Sport at Wimbledon
The crowd are trying their best to show Novak Djokovic their support.
They don't want this match to come to an early end because of injury.
Auger-Aliassime 5-5 Djokovic*
Tim Henman
Former British number one on BBC Two
You could tell what that meant to Felix Auger-Aliassime just by his reaction.
He was down 15-40 and won four points in a row to show some more resilience in this first set.
Auger-Aliassime 5-5 Djokovic*
The calf problem is particularly bothering Djokovic when he serves - both propelling himself into the air and then on landing.
Auger-Aliassime 5-5 Djokovic*
Unreal ace from Felix Auger-Aliassime. And then another!
Superb response from 15-40 down to hold.
Image source, Getty Images*Auger-Aliassime 4-5 Djokovic
Beware the injured tennis player?
Novak Djokovic puts a smash away - at a second attempt - to bring up two set points...
The first one goes begging via a backhand that flies just long. And a big serve helps Auger-Aliassime save the second.
*Auger-Aliassime 4-5 Djokovic
Tim Henman
Former British number one on BBC Two
Novak Djokovic still isn't looking totally comfortable.
He is flexing and stretching that calf...
*Auger-Aliassime 4-5 Djokovic
A big cheer erupts as Novak Djokovic emerges from the changeover.
Of course, he's actually just a break of serve away from winning the first set.
And errant forehands like the one Felix Auger-Aliassime just ballooned out of court will help...
*Auger-Aliassime 4-5 Djokovic
Felix Auger-Aliassime is keeping himself warm while Novak Djokovic is being treated.
There's a bit of a worried low hush around Centre Court - the crowd will have been really looking forward to this quarter-final.
*Auger-Aliassime 4-5 Djokovic
Todd Woodbridge
Former Wimbledon doubles champion on BBC Two
Novak Djokovic gave a big reaction to whatever the problem is when he hit that backhand down the line at 0-15. He gave a bit of an 'Oooh'.
From the way he is stretching, it looks like it could be the calf or the Achilles or potentially the plantar fascia area of the foot itself.
They are testing the stability of the ankle into the calf at the minute, which isn't a good injury. It is one you tend to get at the backend of your career rather than at any other point.
BBC One: Auger-Aliassime v Djokovic. BBC Sport.
Watch here at 19:00
