Well, well!

Fernandez will get another chance to break after a punchy return that Sabalenka slaps long.

Ooof! What a huge serve from Sabalenka, almost ripped the racquet right out of Fernandez's grasp.

Wonderful retrieving from Fernandez, scurrying side to side before Sabalenka goes wide.

Break point for the 19-year-old.

Fernandez keeps the ball in play with a looping effort that makes Sabalenka think but the second seed races on to a forehand winner and then screams "come onnnnn!'.

The Belarusian is cranking up the volume, but jabs a volley wide before double faulting. Deuce.

Sabalenka goes dancing towards the net but misjudges her volley and then gives herself a little tap on the face in the way of a telling off. She cannot get near the next one, a backhand from Fernandez that barely rises above the tape.

Fernandez mixes it up wit a deft slice, Sabalenka reaches it but the Canadian is waiting to prod a simple volley into the space vacated by her opponent. A solid hold to love.

Naomi Broady
British player on BBC Radio 5 Live

It's such natural power that comes from the racquet of Leylah Fernandez. She absorbs the pace that comes off the racquet of Sabalenka, takes it in here stride and dominates the ball back.

Sabalenka is very intense out on the tennis court. She decided she'd had enough of her racquet, chucked it to the side and since then her level has changed.

But we've said the same with Emma Raducanu - it is the composure of these young players at the big moments that is so impressive.

Big second serve from Sabalenka! That one kicked up off the line too, and then she almost has Fernandez doing the splits beyond the baseline. 30-30.

The 23-year-old blunders down a huge forehand and then an ace to hold from 0-30 down.

Vicious. Fernandez pounces on a second serve to whip away a superb winner and follows it up with another screamer off the next. 0-30, time to make her move in the deciding set?

Leylah Fernandez edges to 30-0 before a punchy Aryna Sabalenka return forces her narrowly into the tramlines - the Canadian isn't deterred, she picks out the spot she wanted just inside the line off her next point, coaxing a forehand winner beyond the Belarusian.

A good hold.

You can feel the tension now.

Not that Aryna Sabalenka is showing it with serves like that, a couple of wrist-rattlers and racquet-twisters from the second seed, before Leylah Fernandez manages to get strings to the fluff.

The second seed responds with a fizzing ace to hold.

Cheers around Ashe as Sabalenka slaps long. Can Fernandez close out the hold? Yes! An in-swinging serve and the Belarusian jabs it back into the net.

Great baseline hitting from the 19-year-old to force Sabalenka into the tape but the next return is an absolute missile that Fernandez can only coax into the tramlines. Deuce.

So who will hold their nerve and book a place in the US Open final?

Aryna Sabalenka broke Leylah Fernandez immediately in the opening two sets, but the Canadian canters to 30-0 in this one - only to then double fault!

She only needs the one!

This semi-final is going to a decider.

Image source, Getty Images

A sigh rings out around Ashe as Fernandez cups a forehand into the net from mid-court, the Canadian then goes long on the back of some punchy work from Sabalenka.

And how about that! Fernandez volleys long. Three set points for the second seed.

So Aryna Sabalenka has the chance to serve out for the second set and level up in this semi-final.

Fernandez staves off the first but then loops a backhand long and Sabalenka breaks!

Ooh, a touch long from the Canadian and that's two break points in Sabalenka's favour.

Brilliant from both players, every stroke had the crowd gasping in anticipation, and eventually it is Aryna Sabalenka who whips a winner beyond a stranded Leylah Fernandez.

The 19-year-old hits back with a punchy forehand winner of her own but cannot pick a backhand up over the tape from the baseline. 15-30.

A wicked return from Leylah Fernandez and Aryna Sabalenka can only find the tape, but the Belarusian has her eye in off the next with a sweeping forehand winner that kisses the chalk.

A leaping second serve outfoxes the Canadian and a Sabalenka forehand rocket is followed by an ace for a speedy hold.