A forehand by Carol Young Suh Lee loops long and Katie Boulter makes sure to slams the door shut with a strong second serve that Lee can only send beyond the baseline.

That 3-0 lead looks very healthy, but it's just the one break of serve that separates the pair as things stand.

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Katie Boulter broke early in the second set, but she allowed Carol Young Suh Lee straight back in. The Briton won't want to make the same mistake again.

Lee has got a half-chance here, though, at 30-30.

Carol Young Suh Lee saves the first break point with a solid serve, but she lets a forehand fly long on the next one.

An early break for Katie Boulter and that should give her a bit of a lift at the start of this deciding set.

Carol Young Suh Lee sends a winner sailing down the line but Katie Boulter replies with an epic cross-court forehand to bring up two break points.

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Huge hitting from Katie Boulter. Carol Young Suh Lee hangs in for a while, but eventually she skews a return wide.

The door opens up for the British number one as Lee goes wide again. 0-30.

More of that, Katie! A superb winner down the line from the Briton gets the third set up and running.

She sends Carol Young Suh Lee the wrong way with another booming forehand on the next point, while the American can't return the following serve.

Aghh. Another double fault. Those keep creeping in for Boulter.

Luckily, it doesn't matter this time as Lee pushes into the net.

Carol Young Suh Lee looks remarkably calm and composed considering this is her first-ever match in the main draw of a Grand Slam.

Katie Boulter has headed off court. This is going to be a tough ask for the British number one now.

She has the crowd against her and Carol Young Suh Lee has all the momentum.

Carol Young Suh Lee misses her first set point, but she brings up another with an ace and Katie Boulter swipes and misses the American's serve down the T.

We're going to a decider, folks.

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Katie Boulter makes the most of a weaker second serve from Carol Young Suh Lee to take control of the point and flick a forehand winner into the corner of the court.

But the ball takes an unfortunate clip off the net cord on the next point and the ball falls outside of the court to give Lee a first set point.

That is not good for Katie Boulter. She'll have wanted to avoid a deciding set at all costs, but Carol Young Suh Lee has the chance to serve out the second set now and level the tie.

Each time Katie Boulter moves ahead in her service game, she either suffers a lapse in concentration or Carol Young Suh Lee comes out fighting to claw her way back.

And that's the last thing the British number one needs. A double fault and it's a break point for the wildcard.

Katie Boulter reaches a drop shot and tries to lob Carol Young Suh Lee, but she doesn't get enough height on the ball and the American wildcard slams a winner into the empty court for a 40-0 lead.

Boulter comes up with her own drop shot to claw her way back to 40-30, but she shanks a return into the stands and Lee moves ahead once again.

Heather Watson
British tennis player on BBC Radio 5 Sports Extra

Katie had such a high first-serve percentage in the first set, over 70%, that I wonder if this was part of her tactics in playing Lee.

But now is the time to start going for it a little bit more and getting some free points.

Another double fault for Katie Boulter moves Carol Young Suh Lee level at 30-all and opens up a half chance for the American.

But two poor misses by Lee and Boulter is let off the hook.

You just start to wonder as this goes on about Katie Boulter's fitness levels. After getting married in July, she hasn't racked up many matches - losing in the first round in Washington and Toronto before a second-round exit in Cincinnati.

Carol Young Suh Lee is looking a lot livelier when she moves around the court.

Carol Young Suh Lee wrongfoots Katie Boulter with a clever little sliced volley at the net and she eventually gets another game on the board as her opponent finds pushes the ball into the net.

Katie Boulter had lost a bit of intensity, but she steps it up again and starts hammering the ball over the net.

A bit too much pace on that backhand, though. 30-30.

It feels like Carol Young Suh Lee has really settled into this match now, and she’s not going anywhere. Katie Boulter is going to have to work hard for this one.

Although that was a much more commanding service game for the Briton as she holds to 15.

Katie Boulter can't make the most of the break point and Carol Young Suh Lee reasserts control to grab the hold and move in front for the first time in the match.

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