Marie Bouzkova races through her service game to hold to love.

The Czech 25th seed has now won seven games in a row.

Naomi Osaka is moved across the baseline by Katerina Siniakova and eventually sends a forehand wide for 15-30.

The former world number one finds an angle to force Siniakova into the net for 30-30 and shakes her fist in delight after a miss from the Czech brings up match point.

Katie Smith
Presenter on BBC Radio 5 Sports Extra 2

This one is starting to run away for the British qualifier.

Naomi Osaka will believe that should be that.

The former champion rises to a key moment and swats away another winner to secure the double break and the chance to serve this out for the second time.

Image source, EPA

It's all coming undone for Harriet Dart as she serves another double fault to gift Marie Bouzkova three break points.

Dart fights back to save the first two but she can't rescue the third as she slams a forehand into the net.

It's a long way back from here for the Briton.

Naomi Osaka is frustrated at her failure to put pressure on Katerina Siniakova as she falls 40-15 down on the Czech's serve.

A couple of misses from Siniakova keep the 13th seed interested, however.

A mis-hit from Osaka allows Siniakova another chance to escape - but Osaka volleys in, before repeating that tactic to reach break point.

Marie Bouzkova has all the momentum right now as she consolidates her break with a relatively trouble-free game.

The Czech 25th seed wrapped it up with a magnificent forehand winner down the line from the baseline.

The crowd enjoyed that one.

Image source, EPA

Naomi Osaka saves the first break point with an ace, before making her way back to deuce as Katerina Siniakova misses a backhand.

Another ace - Osaka's 10th of the match - gives the former world number one game point, and she escapes from a really tricky situation to edge closer to victory.

Was that Siniakova's big chance? The past hour suggests we shouldn't try to predict anything.

Pat Cash
Former Wimbledon champion on BBC Radio 5 Sports Extra 2

Once Marie Bouzkova gets on a roll, she can motor through.

With her other Czech players doing well, she will think it is her turn now.

She is so consistent.

Image source, Getty Images

Harriet Dart is struggling with the ball in her hand as she serves her fifth double fault of the match.

Marie Bouzkova then controls a rally from the back of the court, forcing Dart into an error, to earn break point.

Dart can't save it as she slices a forehand tamely into the net.

Just the start to the second set the Briton would have been hoping to avoid.

We could have another twist!

That's long from Naomi Osaka - and that will be two break back points for Katerina Siniakova.

Katerina Siniakova hammers a forehand into the back of Naomi Osaka's court and makes the line for 40-30. A huge shot on a high-pressure point.

The Czech holds to stay alive here.

Katerina Siniakova loses her focus as she whacks a forehand wide, after a member of the crowd disrupts her during her ball toss. That must be the third or fourth time the chair umpire has had to have a word now and it must be really frustrating for the players.

There's trouble for the Czech here at 0-30.

Harriet Dart looks deep in thought during the change of ends as she prepares to fight to stay in the first set.

There's a glimmer of hope at 30-30 after a double fault, but Marie Bouzkova holds her nerve, sealing the set as Dart puts a backhand into the net.

Katerina Siniakova let out her frustration after conceding the early break. She knows what a huge opportunity she has given herself, so immediately going behind is a real blow.

Naomi Osaka looks to the sky with relief after coming out on top in an enthralling point, landing a volley as she comes through from 15-30 down to hold serve for a 3-0 lead.

Harriet Dart is facing some pressure here as Marie Bouzkova takes advantage of some loose serving.

The Czech 25th seed opens up two break points and seals the game when Dart serves her second double fault of the game.

That was disappointing from Dart and Bouzkova will now serve for the first set.

Image source, Getty Images

Naomi Osaka gets fortunate with a bounce off the net cord which leaves Katerina Siniakova scrambling forward.

Osaka shows no mercy, lobbing her opponent to clinch the break, before offering an apology.

After suffering a massive setback in losing the second set, is that the bit of good fortune the 13th seed needs to press on to victory?

Katerina Siniakova faces an important fifth point at 30-30 in her opening service game.

The Czech nets, and Naomi Osaka will have the chance to make the perfect start to the deciding set.

Harriet Dart is showing signs of threatening Marie Bouzkova's serve with a couple of glorious winners.

The Czech 25th seed does come through in the end to hold as Dart skews a backhand wide, but that was more promising from the Briton.