Now the shock really could be on...

A Coco Gauff double fault sets up two break points for Dayana Yastremska and the American nets a drop shot to give up the early break.

Alexandre Muller double faults and then sends a forehand wide to give Novak Djokovic a three-point lead in the tie-break.

Novak Djokovic's 13th ace of the match helps him into a 3-2 lead in the tie-break.

Jess Anderson
BBC Sport at Wimbledon

Coco Gauff returns to court to a warm round of applause. Dayana Yastremska does a few stretches at the baseline.

This could get really interesting.

Both players have held serve on the opening three points, with Novak Djokovic on serve.

Tracy Austin
Two-time Grand Slam champion on BBC TV

Can Dayana Yastremska keep this level up?

If she played at this level, she wouldn't be ranked at number 42 in the world.

Alexandre Muller holds to send the second set to a tie-break.

Tracy Austin
Two-time Grand Slam champion on BBC TV

Coco Gauff can serve such beautiful first serves but then, out of the blue, the double faults show up.

That was quite a dramatic set. The twists and turns, ebbs and flows and so much of it on the racquet of Dayana Yastremska.

We have seen this from her before and she can play at such a high level.

Jess Anderson
BBC Sport at Wimbledon

Very well played Dayana Yastremska.

Coco Gauff swiftly departs after losing that opening set, no doubt needing a word with herself.

Dayana Yastremska is a set to the good!

We've already seen the number three seeds in the men's and women's draws go out today - is an even bigger shock brewing under the roof on Court One?

Simple as you like from Novak Djokovic, who comfortably holds and asks for an ice towel at the break as Alexandre Muller prepares to serve to stay in the second set.

Ohhh, a dream of a return from Dayana Yastremska! A serve out wide from Coco Gauff, but Yastremska crashes a forehand down the line to take full control of the breaker at 5-2 up with two serves to come.

Gauff is hanging in there, though, a super lob keeping her in with a shout, but Yastremska wins the next and has three set points...

Brilliant from Alexandre Muller.

He saves three set points to stay in contention in this second set.

Novak Djokovic looked home and dry but took his eye off the ball at the worst possible moment.

Coco Gauff is all over a second serve from Dayana Yastremska and unleashes a forehand which earns her that mini-break back.

But then she gives it straight back with another double fault!

Tension, tension, tension...

Coco Gauff gives away a free point towards the start of the tie-break, double-faulting with the second of her first two serves.

Advantage Yastremska early on, with seven points the target.

Andrew Castle
BBC Sport tennis commentator on BBC TV

Novak Djokovic is 38-years-old, you don't keep doing this hour after hour, all that working off the court and that's what amazes his fellow professionals more than anything, that he still wants to.

Dayana Yastremska goes for a bit more on some of her groundstrokes, knowing she's got a bit of a free hit on Coco Gauff's service game.

But the radar is slightly off - a tie-break it is.

Tracy Austin
Two-time Grand Slam champion on BBC TV

That was a remarkable service game from Dayana Yastremska.

I thought the time and the moment had passed after losing three consecutive games.

At the very least, Dayana Yastremska will be in a tie-break at the end of the first set - although there's sure to be disappointment after double-faulting on set point in her previous service game.

Andrew Castle
BBC Sport tennis commentator on BBC TV

Alexandre Muller is making of a match of this.

It's all very well for us to sit here and think it is all one-way traffic, but he is 41 in the world and number 4 in France. He has also won a tour title this year.

He is a very fine player but it doesn't always look like that when you're up against the best of all-time. He is well capable of putting a couple of heavy strikes in.