Jannik Sinner has definitely got a read on Jan-Lennard Struff's serve.

Down 15-30, Struff tries the serve and volley but plants his effort into the net off a heftily-struck backhand return from Sinner.

John McEnroe
Three-time Wimbledon singles champion on BBC Two

If Jannik Sinner is going to take three or four steps back to receive off Jan-Lennard Struff, he better start hitting that return deep.

His opponent will make him pay for doing that today.

Much better service game from Coco Gauff.

Two big serves get her up 30-0, she's more than capable but it's the inconsistency that hurts her.

Still, she puts away a volley at the net and this set isn't gone just yet.

Jessica Pegula is going to have to serve it out.

Jessica Pegula is closing in on this first set.

She has been the more controlled of the two Americans thus far, perhaps that one oddly passive service game aside.

Coco Gauff gave herself a chance at 15-30 but Pegula remained focused and calmly secured the hold.

Image source, Getty Images

Jannik Sinner eases through a hold to 15, sealing it with an ace down the T.

Emily Salley
BBC Sport at Wimbledon

Uh oh. Right in the middle of a lengthy rally, a stray ball rolls onto the court and stops Jan-Lennard Struff in his tracks.

"Let," says the umpire. "Replay the point".

That might just have worked in the German's favour, helping him fend off the break point and hold.

Jan-Lennard Struff comes up with a couple of first serves to navigate deuce. He's had a huge stroke of fortune at the start of this second set.

Harry Poole
BBC Sport at Wimbledon

As I was saying...

Best get ourselves settled in for a bit of a rollercoaster here, I reckon.

What did Harry just say about Coco Gauff putting her fans through the wringer?

No sooner has she broken back, she hands the advantage right back to Jessica Pegula.

A double-fault is a fitting way for that game to end. Two breaks of serve for Pegula so far but Gauff will feel they have been far more about her serving than anything special from her fellow American.

Image source, PA Media

Ooooh a let-off for Jan-Lennard Struff as a ball falls out of his pocket midway through a lengthy baseline exchange. He was firmly on the back foot in that rally.

They replay the point and Struff comes up with a big serve which Jannik Sinner returns wide.

Double fault and an ace down the T to open the second set from Jan-Lennard Struff. 15-all.

Jannik Sinner reads a smash, forces Struff to attempt a second, and the German puts his overhead into the tramlines.

Struff takes a big deep breath and finds a hefty wide serve. 30-all.

And then, he messes up a serve and volley, unable to ping Sinner's low return back over the net.

Harry Poole
BBC Sport at Wimbledon

Coco Gauff doesn't half put her supporters through it.

The 22-year-old doesn't tend to hide her emotions, and her frustration was clear after she made that a horrible miss at the net to gasps from the crowd. It looked like a sure thing.

It's been an impressive response since, however. She hints at her growing confidence with that big return to break back.

Cheers on Centre Court as it appears Gauff has arrived in this contest.

Just like that, Coco Gauff breaks back.

Jessica Pegula looked off it that whole game and Gauff took full advantage.

The seventh seed meant business while Pegula's backhand into the net down 0-40 looked very weary.

We're only six games in!

Image source, Getty Images

Emily Salley
BBC Sport at Wimbledon

Jannik Sinner looks up to his team and gives a slight shake of his racquet after wrapping up the opener.

He hasn't done anything spectacular yet, but he hasn't needed to and the Italian strikes just at the right moment.

John McEnroe
Three-time Wimbledon singles champion on BBC Two

Jannik Sinner loves that serve on the advantage court out wide. It is so tough to handle for any opponent.

This is exactly the match he would've expected to be playing. He just needed to keep his cool, wait for his opportunity and jump on it - and he did that.

What does that do to Jan-Lennard Struff, having played all that tennis? Will he let down a little bit or will he keep up this effort? It won't be easy for him.

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

These two decided that doubles wouldn't be a part of their major tournaments. I think that was a good call from them. It's just a part of tennis, playing your friend.

Jan-Lennard Struff drags his backhand wide to hand Jannik Sinner the opening set.

Barely 15 minutes ago, the Italian was down 5-4 and coming into a key service game off the back of three sketchy holds. But he came through with a hold to love and then made the crucial break.

How Struff must be ruing those three wasted deuces.

Image source, Getty Images

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

I like the play from Gauff. Especially when your forehand feels horrible, you want to play as close to the net as possible.

A smidgen of pressure on Coco Gauff as she puts an overhead volley into the net to go down 15-30 on serve.

She responds well, though, a couple big serves get her out of trouble before Jessica Pegula hits tamely into the net.

Pegula stays just the solitary break up.