Solana Sierra seems to have forgotten that Coco Gauff's backhand is causing all the problems. Sierra serves to that side and then is unable to get the ball back over the net.

Solana Sierra looks on track to wrap up a pretty comfortable hold of her own at 40-15 but Coco Gauff isn't backing down.

Gauff closes the gap with a lovely forehand that skips up off the baseline before Sierra puts into the net for deuce.

Neither player can grab hold of this set. Jannik Sinner's first serve goes AWOL at the start of the fourth game and when his drop shot, from behind the baseline, drifts into the tramlines, he's staring at a 0-30 deficit.

No matter. Ace. Long forehand from Nuno Borges. Ace. Netted backhand from Borges.

We have a hold of serve on Centre Court. This is not a drill.

John McEnroe
Three-time Wimbledon singles champion on BBC One

That was really exceptionally well done to get the break right back.

Remember, he didn't have a tune-up tournament at all. Hadn't played a match since that second-round loss against Cerundolo. He is finding his game, his rhythm, it appears to me.

Image source, PA Media

Coco Gauff looks like she's found her groove on serve.

The American races to a 40-0 lead and then powers through an ace to get the hold.

Solana Sierra gets to advantage but can't close out the game as a loose drop shot clips the net and lands short.

Sierra takes her chance at the second attempt when a stooping Coco Gauff skews a forehand way off court.

Pat Cash
Former Wimbledon champion on BBC Radio 5 Live

Jannik Sinner hasn't come out of the blocks, like we've seen before, but he is still playing well. You can see he is a bit frustrated with some of his forehands because he isn't quite timing them how he normally does.

Full credit to Nuno Borges because he has been playing very well. He is getting his opponent on the run and serving very well, but a few errors are creeping in now.

Jannik Sinner ROARS as he lands a backhand winner with Nuno Borges up at the net.

Back-to-back-to-back breaks to start this third set. Chaos.

It's beautifully defended by Solana Sierra.

The Argentine sends Coco Gauff from corner to corner as she edges to the net and eventually slams away a winner for deuce.

Errors, errors, errors. Nuno Borges presents Jannik Sinner with a break point.

Huge sigh of relief for Nuno Borges. He and Jannik Sinner enter into close combat at the net, the ball pinging between them, before Borges goes for the kill and just clips the baseline with his forehand.

A thoroughly entertaining point - 15-30.

He extends his lead with a smash but Sinner claws his way back.

John McEnroe
Three-time Wimbledon singles champion on BBC One

He will be fuming. He has just given this guy hope when it was evaporating.

Unbelievable he just gave him that game back.

Image source, PA Media

Coco Gauff has another opportunity to take control of this opening set after Solana Sierra's forehand strays long.

After losing her previous service game, Coco Gauff goes back to basics and it pays off.

A comfortable hold to 15 keeps this opening set on serve.

Ace. Double fault. Nuno Borges breaks right back. That was unexpected.

That's a poor leave from Jannik Sinner. He pulled out of his backhand volley but Nuno Borges' shot landed comfortably inside the baseline. 0-15.

With a loose forehand, the Italian is down 0-30.

A double fault. 15-40.

A messy start to the third set from both players.

Solana Sierra gets the hold after Coco Gauff gets her angles wrong and sends a forehand wide of the paint.

Great resilience shown from Sierra to come through that game after trailing 30-0.

Emily Salley
BBC Sport at Wimbledon

Ah. It felt like Nuno Borges really had a chance of springing a shock result on Centre Court, but it feels like any momentum that he once had is gone.

The Portuguese player is looking more and more frustrated in between points and he gives his bag an angry smack when he returns to his chair.

John McEnroe
Three-time Wimbledon singles champion on BBC One

This could be curtains here losing this point. This set could get away in a hurry.

Borges should have won that game, now he is in huge trouble. If it wasn't bad enough at two sets, to get broken in the first game.

If the [negative thoughts] weren't there before they will be now humming in his brain.

Coco Gauff's backhand is causing some major problems for Solana Sierra. The American makes a positive start to lead 30-0 against the serve, but Sierra starts to target the forehand and gets enough joy to win three successive points.

Gauff refuses to let the game completely get away from here and gets to deuce.