Jan-Lennard Struff is showing no signs of fatigue despite spending more than 14 hours on court, charging from one side of the baseline to the other to hunt down a Jannik Sinner drive volley. Alas, his skied reply lands wide. 30-0.

He pulls one point back but with an ace out wide, Sinner has two set points.

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Jessica Pegula is playing with real confidence here.

Another comfortable hold, the highlight of which is another fine passing shot, fired down the line on the backhand.

Ace. Ace. Two break points saved in the blink of an eye.

But then Jannik Sinner steps into a second serve, taking the ball on the baseline with both feet off the ground, and wipes a cross-court forehand winner.

Huge.

Greg Rusedski
Former British number one on BBC Radio 5 Live

It seems like all of a sudden, Sinner is reading the serve of Struff. This is where you separate the boys from the men, I expect Sinner to lift his game right now.

Jannik Sinner pounds a forehand winner. 0-15.

Jan Lennard-Struff follows a serve into the net, tries to take Sinner's return out of the air - his racquet high up on his backhand - and puts the ball into the net. 0-30.

Sinner wallops a return. 0-40.

UH OH.

Coco Gauff is on the board.

After showing us example of her weaknesses early on, she shows the skill that helps her to overcome them here.

Jessica Pegula must have thought she'd hit a winner when she lasered a backhand return down the line but Gauff just about gets it, jabs her racquet down and somehow gets the ball cross-court, just over the net to win the point.

Image source, PA Media

John Lloyd
Former GB Davis Cup captain on BBC Two

Jan-Lennard Struff is way better than his ranking on grass. I don't understand why he hasn't done better at Wimbledon, to be honest, considering the game he has got.

He has had the tendency to serve double faults on big points in the past, but he seems to have corrected that so far in this tournament. I do think his whole mental attitude has changed recently, I think he sort of gets the game now at 36 years old.

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A routine hold to love for Jannik Sinner, finding some first serves at last.

He looks up to his box and shakes his racquet with a look of determination.

Pam Shriver
Five-time Wimbledon doubles champion on BBC Radio 5 Live

Pegula was my pick to win, pre tournament. But, the way Naomi Osaka played the other day...

Harry Poole
BBC Sport at Wimbledon

Issues on serve - and especially her tendency to double-fault in key moments - has long been the biggest obstacle to progress for Coco Gauff.

Although a two-time major winner, that problem very much remains as we’ve just witnessed in the opening game.

There are groans in the crowd as she falters to lose serve from 40-0, followed by shouts of encouragement. That was absolutely not the start she needed here against top-ranked American Jessica Pegula.

Emily Salley
BBC Sport at Wimbledon

Jannik Sinner wastes no time in getting an ice towel wrapped around his neck as soon as he sits down.

The Italian has a tendency to struggle in the heat, so it will be interesting to see how he copes this afternoon with temperatures set to reach at least 30C.

Pat Cash
Former Wimbledon champion on BBC Radio 5 Live

Gauff is such an incredible athlete and competitor but we all have our weaknesses, we somehow have to work with them and around them.

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Jessica Pegula holds with a minimum of fuss.

A lovely cross-court passing shot gets things started and a smart drop shot takes her to game point before Coco Gauff fires long.

At 15-all, Jan-Lennard Struff glides forward and plants a routine volley into the base of the net.

He responds with an ace and clenches his fist enthusiastically as Sinner sends a forehand long off a second serve.

Ace to hold. More fist pumping at the change of ends.

Pam Shriver
Five-time Wimbledon doubles champion on BBC Radio 5 Live

One thing about Coco Gauff, she can win majors without her best game.

John McEnroe
Three-time Wimbledon singles champion on BBC Two

Jannik Sinner had a string of missed first serves there. Jan Lennard-Struff tried to take advantage by being aggressive off the second serves, as he should.

It is a service hold but it is a little worrying to see Sinner looking vulnerable on serve in the early stages.

Image source, PA Media

We're under way on Centre Court and what had looked a straightforward service game for Coco Gauff quickly becomes very sticky.

A double fault gets Jessica Pegula on the board and a couple of loose forehands later, it's deuce.

Gauff then plants a backhand into the net before another double fault gifts Pegula the break.

An early advantage for Pegula and she didn't really have to do a whole lot to get it.

In his past three service games, Jannik Sinner has invited pressure on himself with runs of errors to throw away 40-0 and 40-15 leads.

On all three occasions, he's been aided through deuce by errors from his opponent. If Jan-Lennard Struff had been more clinical, the first set would be over and done with.

Pam Shriver
Five-time Wimbledon doubles champion on BBC Radio 5 Live

Given Pegula's record, it's quite unbelievable that this is her Centre Court debut, at 32.

Image source, Getty Images

Another scratchy game from Jannik Sinner, who isn't landing many first serves and is having trouble with the depth and pace of Jan-Lennard Struff's returns.

From 40-0, he's dragged back to deuce.