Coco Gauff attacks Madison Keys' second serve and powers a winner down the line.

Keys led 4-1 in the first set before eventually going on to win a tie-break and now finds herself on the opposite side in the second...

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Fine work from Coco Gauff as she waits patiently for the ball to land after sitting up off the net cord. Gauff whips it cross-court and out of Madison Keys' reach - 15-15.

Keys' forehand slaps into the net and Gauff has two break points.

Coco Gauff stands up the challenge to hold.

A 37th unforced error of the match from Madison Keys puts Coco Gauff firmly in control of this game - leading 40-15.

But as we've seen so many times in this encounter, it swings in the other direction with Keys collecting three points in a row to get a look at break.

Coco Gauff secures the break at the second time of asking as Madison Keys' forehand lets her down once again.

Neither player has been at their best so far in this match but it has been an intriguing watch.

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Andrea Petkovic
Former world number nine on BBC Radio 5 Sports Extra and BBC Sounds

Well this match hasn't got better for either player.

You can just feel the nerves and the big occasion for both players here, even though they have had huge successes in the past. I think it's because they are friends playing for such a big moment.

Even though we haven't seen the best tennis from these two yet, this match is still very intriguing.

Coco Gauff sends Madison Keys deep into the corner and follows with a whipping forehand on the opposite side.

Keys finds the net and Gauff has a couple of break points.

Now it's Madison Keys' turn to slip up and Coco Gauff gets the hold.

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It took Coco Gauff four attempts to get her first hold of serve in the first set, she can't afford to let Madison Keys build up a head of steam like that again in this second.

Gauff is on the verge of holding but a couple of forehand errors invite Keys back into the game.

Madison Keys nestled a forehand right on the line. Coco Gauff suggests it was wide and the umpire comes across to take a look but it's deemed in.

Gauff battles back to deuce but another unforced error opens up the chance for Keys to hold.

Keys finally gets it after a back-and-forth seven-minute game.

Andrea Petkovic
Former world number nine on BBC Radio 5 Sports Extra and BBC Sounds

In the last five or 10 minutes, Coco Gauff has been doing something that I haven't seen her do on clay lately.

She is lifting her left foot up when she is hitting her forehand, which of course has a lot to do with the power of Madison Keys' shots. It is a technical issue that usually comes through on quicker surfaces usually and not so much on clay.

Something seems to be off with her serve and forehand on this clay court...

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Madison Keys again responds well for deuce but a loose forehand ends up wide.

Coco Gauff has a fourth opportunity to break in this opening game of the second set but it's wasted.

Madison Keys digs in and a couple of forehand winners draws her level at deuce.

But Keys can't make it three points in a row and Coco Gauff has another early look at break.

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The first set was so unpredictable, swinging one way and then the other, how will this second get going with Madison Keys on serve?

Gauff settles in and has two break points.

Andrea Petkovic
Former world number nine on BBC Radio 5 Sports Extra and BBC Sounds

That was a nervy first set - you could see the nerves of both players.

Madison Keys was up 4-1 and at 40-15 to go up 5-1 she started to become nervous, and now we have seen the same from Coco Gauff who was in control of the rallies in that tie-break.

But Gauff's downfall this season has been those double faults. She thinks she is in control of the match and then she just gives it away.

Madison Keys gets it done.

What a relief for the Australian Open champion.

She was 4-1 up and led 40-15 at one stage in that opening set and eventually had to get the job done via a tie-break.

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Coco Gauff pulls off a remarkable shot - fizzing it just over the net and getting the ball to spin away.

But another double fault - Gauff's third in the tie-break and seventh in the match.

Keys will serve for the set.

Madison Keys puts everything into a string of forehands and it eventually wears Coco Gauff down.

Gauff gets under the ball and it loops long.

Keys has set point.

A second double fault of this tie-break from Coco Gauff allows Madison Keys to draw level.

Keys fails to capitalise fully, though, and a forehand into the net sees Gauff back in front.

Coco Gauff keeps asking questions with solid returns and eventually Madison Keys folds with a forehand into the net. That's the second time Keys has been broken in this tie-break.

Much better from Keys down the line.