Chanda Rubin
American former world number six on Radio 5 live

You look at Simona Halep, and there is despair on her face. Sloane Stephens has a clear game plan but I haven't quite seen that from her opponent.

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Joel Newnham: What's Simona meant to do? Out of options

My Bay: Stephens is not making Halep run. But is surely making her get forced errors.

Stephens can do no wrong. She finds herself 0-30 down but hits a forehand passing winner and then lands a mis-hit plum on the line.

Halep is left stranded. You could see the optimism drain out of the world number one as the ball landed. A huge exhale of breath, her eyes dropping to the floor. Can she turn this around?

Stephens holds.

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Chanda Rubin
American former world number six on Radio 5 live

You have to embrace the pressure, sometimes it's a battle within yourself to enjoy it. When Sloane Stephens gets to a final, she raises her level and, right now, she has an answer for everything Simona Halep is throwing at her.

She's. Just. So. Quick.

Sloane Stephens is absolutely everywhere here and picks up a short ball off the dirt and plays a beautiful angled shot of her own. That brings up a fourth break point.

This time Stephens gets there on another lung-buster of a point.

Stephens now leads by a set and a break. One hand on the trophy?

Both break points are seen off by Halep but here's another...

Forehand winner by Halep.

Back to deuce.

Crucial, crucial moments...

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Stephens is back in the groove instantly. There's no easy start to the set for Halep.

The American has two break points to strike a crucial blow early on in the second...

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Don Wimble: Really want to see Halep get her 1st slam here, but Stephens has brought the good stuff today. Great final already.

Bolanle Adebola: I want, need, crave 3 sets of this!!!

Chanda Rubin
American former world number six on Radio 5 live

Sloane Stephens is so athletic and strong but she is a beautiful mover. She would expect Simona Halep to be more comfortable on clay because she has grown up on it but Stephens looks less rushed.

This has been the match of the tournament by a distance. Both players are performing at some level but Stephens looks as good as I've ever seen her.

A quick breather for the players and the fans before we get under way again.

As good a first set as you'll see.

Sloane Stephens takes the opener.

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Into the net from Halep.

To deuce we go.

That's Simona Halep at her best. The Romanians in the crowd on their feet, waving their flags.

She earns herself a first break point at a crucial time.

Both players are groaning and grunting now. The rallies are brutal. It's so good to watch but must be horrible on the legs to play in.

Halep levels at 30-30 with Stephens serving for the set.

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Sloane Stephens' support team are on their feet in the stands. Halep just can't find a way through the American's defence and then Stephens turns the tables and gets herself on the attack.

Now a thumping forehand at 90mph. Huge.

30-15.

That's a good point, Jiten. Murray lost four finals before winning his first Grand Slam at the US Open in 2012. Halep is currently on three losses but will join Murray on four final defeats if this match continues the same way.

Halep holds Stephens off for now. She ensures the American will have to serve it out.

Chanda Rubin
American former world number six on Radio 5 live

Sloane Stephens is a person who likes to laugh, doesn't like to feel pressure so she does anything she can to relieve it. Remember when she lost eight straight first rounds after the US Open win, she was just "relax" to everyone, and look where she is now.

Paul Staveley: This is a brutal contest so far and Stephens has hit some unbelievable winners. Halep is going to have to find a way to unnerve her if she’s going to have any joy here. Maybe the high bounce is going to be her way in.

Jiten Chandarana‏: Halep's story reminds me a bit of Andy Murray's. Grand slam finals but not getting over the line. Of course, Murray did eventually, and I believe Halep will too. Maybe today.

That's the first sign of frustration I have spotted from either player. Halep slaps her racquet angrily as she misses a forehand after creating an opportunity.

Both players have shown incredible movement so far but Stephens seems to have bigger weapons, particularly on the forehand.

Another couple of winners comes from that wing and now another clench of the first. The American is a game away from this first set.

Image source, Getty Images

Chanda Rubin
American former world number six on Radio 5 live

When you keep losing Grand Slam finals, it definitely creates scar tissue. It's hard to get beyond, when you have suffered some bad moments, but Simona Halep is trying to do that.

Still a break down, this is going to be a major test for her.

Image source, EPA