Oh dear. A wild mishit from Carlos Alcaraz flies wide and pulls Alexander Zverev level at 15-15.

The German fourth seed gets the next point too with a nice backhand drop shot that pulls Alcaraz in and leaves an empty court to fire into.

Carlos Alcaraz is back up on his feet and he tests out his leg with a quick jog to the back of the court, where he awaits Alexander Zverev's serve.

Annabel Croft
Former British number one on BBC Radio 5 Live

This is not a great sign for Alcaraz because that was a poor last game just as he was building momentum.

Jonathan Jurejko
BBC Sport at Roland Garros

Carlos Alcaraz has called the trainer out.

A towel goes over his left thigh before the physio stretches the player's leg out.

That becomes a medical time-out.

Greg Rusedski
Former British number one on BBC Radio 5 Live

This is just so nervy from Alcaraz. His feet have stopped moving and he's so flat footed.

And he gets it on the first go.

Carlos Alcaraz finds the fence and Alexander Zverev finally gets himself on the board in this fourth set.

He's still a break down, though.

Image source, Getty Images

The German fourth seed has two break back points.

Alexander Zverev managed to come back in that last set, but it's going to take a miracle do it again in this one.

David Law
Commentator on BBC Radio 5 Live

This is a masterclass from Carlos Alcaraz!

Image source, Getty Images

And there it is.

A delicate drop shot winner from Carlos Alcaraz, who holds up a clenched fist. The Spaniard looks unstoppable at the moment.

It goes from bad to worse for Alexander Zverev.

Another double fault gives Carlos Alcaraz the chance to get the double break.

Annabel Croft
Former British number one on BBC Radio 5 Live

Zverev looks like he doesn't really like to generate the pace off those slower balls.

That is delightful from Carlos Alcaraz, who slows down play with a high looping forehand before fizzing one down the line.

Then it's Alexander Zverev's turn to fire home a winner. 30-30.

Annabel Croft
Former British number one on BBC Radio 5 Live

I feel like there's something different about the way Alcaraz is hitting the ball right now.

This has been a dreadful start to the fourth set for Alexander Zverev.

The Olympic champion double faults. 0-15.

Annabel Croft
Former British number one on BBC Radio 5 Live

That is so much better from Alcaraz. Maybe this is his patch of time where he's going to start playing his best tennis.

This match is going from one extreme to the other.

A minute ago, it was Alexander Zverev on top. Now it's Carlos Alcaraz who is flying.

The Spanish third seed backs up the break, racing to a hold to love.

Annabel Croft
Former British number one on BBC Radio 5 Live

That's the first sign of real emotion from Carlos Alcaraz and that might release him a little bit.

What a way to break!

Carlos Alcaraz looks like he's out of it as Alexander Zverev's large figure looms at the net, but the Spaniard swerves it around the German and it just catches the baseline.

Incredible.

Image source, Getty Images

Carlos Alcaraz misses the first break point. Can he get the next one?

Image source, Getty Images