Greg Rusedski
Former British number one on BBC Radio 5 Live

Struff is serving exceptionally well, he's had a good balance of coming forward. Sinner has not found his rhythm yet and he's not getting into Struff's serve.

Tracy Austin
Two-time Grand Slam champion on BBC Two

There is a real difference in trajectory between Coco Gauff and Jessica Pegula's forehands.

Pegula is able to hit deep on the return and really use her forehand to be so lethal. She loves the cross-court shot but she can also direct it down the line. She has such good technique because of her great footwork and great spacing, which means she can swing freely and really drive through the ball.

Gauff hits her forehands a little too short sometimes, so it will be important for her to hit with depth to dictate play and challenge Pegula's timing. Her coach is trying to get her to drop the racquet head more and drive through her forehands into her left shoulder more.

Big serves, short points. Jan Lennard-Struff holds to love. He's only dropped two points on serve - both in the opening game.

Jannik Sinner has an ice towel around his neck at the change of ends.

Once again, Jannik Sinner breezes through deuce but that's twice now that he's come under a bit of pressure on serve.

He led 40-0 in his previous service game and 40-15 in this one.

Image source, Getty Images

Emily Salley
BBC Sport at Wimbledon

There's a slight delay before Jannik Sinner steps up to serve, which causes some confusion around Court One.

But it all becomes clear when the umpire points to a little bird on Jan-Lennard Struff's side of the court and the crowd start chuckling as it's chased away by a ball kid.

Jessica Pegula and Coco Gauff emerge on Centre Court and are greeted by enthusiastic applause.

But with their big over-ear headphones on, I doubt either of them heard it!

Headphones off, Pegula wins the toss and chooses to receive first.

Image source, PA Media

We've been asking for your questions during Wimbledon and following the high temperatures at SW19 yesterday, Tony in Essex asked this via the Get Involved link:

Why don't they close the roof on Centre Court and Court One with the temperatures so high?

We put the question to the All England Club, who responded:

Wimbledon is an outdoor tournament and therefore the roof is only closed during rain delays or when it becomes apparent that the match will not finish in natural light.

There is a heat rule and measures that can be enforced to keep players safe if deemed necessary - you can find out more about that in this article from the BBC's Ask Me Anything team.

Well! Jan-Lennard Struff belts a deep return which catches Jannik Sinner flat-footed and the Italian's reply goes into the net. 0-15.

Sinner tries to come on the approach but is driven back behind the service line by a moon-ball return. Struff's good work is undone by a shanked forehand.

At 40-15, Struff advances on the net and punches home a deep backhand volley winner before an iffy bounce does for Sinner, swinging over the ball, to bring up deuce.

John McEnroe
Three-time Wimbledon singles champion on BBC Two

I know Jannik Sinner rarely body serves, but to me that would be a good play against Jan-Lennard Struff because he likes standing in close.

Tracy Austin
Two-time Grand Slam champion on BBC Two

I'm very much looking forward to Jessica Pegula and Coco Gauff facing off. They are good friends, they have been doubles partners before and they are both looking to get to the semi-finals here for the first time.

Pegula has been to the US Open final but, at 32 years old, she still hasn't won the major she so desperately wants. This surface suits her style of play, she hits so flat, so hard and so early. She is a really talented grass court player.

Gauff made it to the fourth round at 15 years old, so we thought bigger things were to come for her. She's had her struggles in the matches she has played, but boy does she dig deep.

Back-to-back holds to love for Jan-Lennard Struff. Jannik Sinner is struggling to make a meaningful impact with his returns.

Image source, Getty Images

Great Britain's Alfie Hewett, the second seed in the men's wheelchair singles, has raced through the first set of his first-round match against Dutch opponent Tom Egberink on court three.

You can watch that match in full on the BBC iPlayer.

John McEnroe
Three-time Wimbledon singles champion on BBC Two

Two questions will be asked today.

What, if anything, will the heat do to Jannik Sinner - and will it affect him at all?

How much is left in the tank of Jan-Lennard Struff, who has played a lot of tennis to get here?

Jannik Sinner comes through deuce without incident.

At 40-0, Jan-Lennard Struff finally returns a Jannik Sinner serve into the court.

Sinner manoeuvres himself up to the net and goes for a cute cross-court forehand but doesn't get the elevation.

Two more good returns bring further errors. Good recovery from the German.

Image source, Getty Images

Jessica Pegula had a relatively trouble-free passage through to the second week, beating Darja Vidmanova, Sara Sorribes, and Jessica Bouzas in straight sets, but had to fight back from a set down to beat Iva Jovic in the fourth round.

Pegula only dropped four games across sets two and three after losing the opener 6-4.

Coco Gauff, by contrast, is making a habit of going the distance, playing 21 three-set matches in 2026 and winning 14.

She beat Tamara Korpatsch in straight sets in round one but was taken to deciders by Solana Sierra and Claire Liu before having to recover from losing the opening set to beat Belinda Bencic on Sunday.

The most recent meeting between these two players - won by Pegula in Riyadh last November to extend her head-to-head record to 5-3 - went the distance, so strap in.

John McEnroe
Three-time Wimbledon singles champion on BBC Two

Image source, Getty Images

I would go with Jessica Pegula to edge this one because Coco Gauff isn't quite there with her serve. It is getting there, so she could have a big day but she could also go the other way.

I have to say her forehand still looks a little bit iffy at times as well.

Emily Salley
BBC Sport at Wimbledon

A bottle of fizz pops and the cork hits the ceiling just as Jan-Lennard Struff tosses the ball up to serve.

"No, thank you" a frustrated steward says to the culprits.

It didn't seem to to distract Struff, to be fair.

Tracy Austin
Two-time Grand Slam champion on BBC Two

Jan-Lennard Struff is so inspiring and motivational. He has made his first Grand Slam quarter-final on his 47th attempt at 36 years old.

A lot of his success is to do with his dangerous style of play. He has served 100 aces to get here, so absolutely monstrous serves, and he will have to go big again today. He has a huge forehand, he comes forward a lot which is such an advantage on grass, and he volleys with a lot of technique.

I would consider him a dangerous opponent because he won't allow Jannik Sinner to get a lot of rhythm.

Image source, Getty Images

An equally brisk hold to love for Jan Lennard-Struff, whose highlighter yellow racquet has caught my eye.

Plenty of big first serves from the German, including a 139mph rocket.