John McEnroe
Three-time Wimbledon singles champion on BBC TV

Medvedev is stressing now. I hope the fans that are watching this have enjoyed what they've seen between two guys who have alternately tried to find ways to probe and get their opponent off their game - deal with the stress, the pressure of this situation.

Adapting. It's been an entertaining all-in-all first round match.

We're back under way on Centre Court and Sasnovich produces a lovely drop shot, but one which Serena Williams does not run for.

Now, it's Sasnovich's turn to slip on the grass.

Serena Williams, with a huge cheer from the crowd, is back on court but limping heavily. She is going to give it a try, but how mobile will she be?

We now just sit, wait and wonder. Aliaksandra Sasnovich is on the court, not really knowing what to do with herself as she's the only player out there.

She puts in some serving practice drills, but will she even need to serve again today?

Serena Williams is struggling to put any weight on that ankle. She calls for the trainer, but then, pretty quickly, vanishes off court to get more sustained treatment.

Now it's Daniil Medvedev having to fend off the breaks! But he does, and now the Russian is one game away from the second round...

Seeing the footage again and Williams' left ankle gives way as she tried to produce a return. Then the next time she has to play a shot she is grimacing in pain.

We've had loads of slips on this surface over the past two days and is this going to end Serena Williams' tournament after only five games of match one?

Annabel Croft
Former British number one on BBC Radio 5 Live Sports Extra

Something's troubled Serena. She's definitely not pushing up off her ankles here.

I think she's done something to her ankle.

This is a nightmare for her. I wonder if she landed badly on it

And Serena Williams may have hurt herself and Sasnovich immediately takes the break back. We saw injury drama earlier on, is the same going to happen again now?

Sasnovich has a break point and does Serena Williams have an injury? She's looking down at the ground.

Jan-Lennard Struff is making Daniil Medvedev earn this, the Russian hasn't quite been at his clinical best in the fourth set - the chances have been there. But it's 5-5 in the fourth.

Image source, Getty Images

Simon Reed
BBC Sport commentator at Wimbledon

Listen to the roar as Serena gets the break at the fourth attempt.

The returns don't win the point outright but it sends a message: 'Lady, you're going to have to do better than that.'

Sasnovic goes long with a forehand and that is a great start for Serena Williams as she breaks her opponent's serve at the second time of asking and the first set is hers to lose now.

That third break came and went, but here's a fourth. A stunning two-handed backhand return down the line, brilliant from Williams.

A two-handed cross-court backhand from Serena Williams, but she pulls it wide and she has not taken either of her chances for a break.

But she has another opportunity.

Two break points for Serena Williams in the fourth game after a brutal forehand that gave Sasnovich no chance.

Daniil Medvedev might've been serving for the match now but Jan-Lennard Struff wipes out another sniff of a break for the second seed, coming from 0-30 down to hold and it remains on serve as we motor towards the business end of this fourth set.

Jo Durie
Former British number one on BBC TV

Gauff will be quite relieved she got through that match, most of all her footing and how to move on the grass.

A superb serve down the middle from Serena Williams and Sasnovich can get a racquet to it but can't return and three games in on centre and we're on serve.