Serena Williams beats Karolina Pliskova to reach semi-finals
American 17th seed wins 6-4 6-3 at Flushing Meadows
Argentina's Juan Martin del Potro through to semi-finals on Friday
Third seed beats John Isner 6-7 (5-7) 6-3 7-6 (7-4) 6-2
2017 champion Sloane Stephens knocked out by Anastasija Sevastova
Latvia's Sevastova through to semi-finals with 6-2 6-3 victory
Rafael Nadal plays Dominic Thiem in the last match of day nine
Extreme heat policy in place as New York temperature causes problems
Del Potro 6-7 (5-7) 6-3 7-6 (7-4) 6-2 Isner
What a guy. Does anyone dislike Juan Martin del Potro? If you do, you're wrong.
He's asked what he did in the 10-minute break between sets due to the heat rule.
"I didn't want to come back again!" he laughs.
Del Potro 6-7 (5-7) 6-3 7-6 (7-4) 6-2 Isner
John Isner gets a great ovation from the crowd as he makes his way off court. His wife is due to have a baby soon. Every cloud.
Del Potro looks like a happy school boy as he waits for his post-match interview.
Del Potro 6-7 (5-7) 6-3 7-6 (7-4) 6-2 Isner
Juan Martin del Potro is back in the semi-finals at the US Open! John Isner dumps another into the net and the Argentine is beaming. The former champion is right in with a shot this year.
Both men come together at the net and embrace.
Del Potro then stands in the middle of the court with his arms aloft and looks to the skies.
Del Potro 6-7 (5-7) 6-3 7-6 (7-4) 5-2 Isner*
Here we go.
Three hours and 30 minutes in, Juan Martin del Potro has match point.
Del Potro 6-7 (5-7) 6-3 7-6 (7-4) 5-2 Isner*
It's stand and deliver stuff from both men. They don't want to run. If it's there to hit they'll hit it. If it's not they'll not waste any energy trying.
Deuce.
Del Potro 6-7 (5-7) 6-3 7-6 (7-4) 5-2 Isner*
Double fault from Isner. Both men are limping towards the finish line. Del Potro is on the home straight though. Isner hasn't even made it to the final bend.
30-30.
Del Potro is having his thighs rubbed frantically by the trainer. I'm no doctor but it looks like fatigue.
Isner must hold serve here or he's out.
Del Potro 6-7 (5-7) 6-3 7-6 (7-4) 5-2 Isner*
All is not perfect for Del Potro but he gets through. He bangs a few more heavy forehands but hardly moves when a counter-punch from Isner flies by.
Here comes the trainer again.
Regardless, Del Potro is one game away from the semi-finals.
*Del Potro 6-7 (5-7) 6-3 7-6 (7-4) 4-2 Isner
A 129mph serve from DelPo. His fans can breathe a little easier.
15-0.
Now another thunderbolt.
30-0.
*Del Potro 6-7 (5-7) 6-3 7-6 (7-4) 4-2 Isner
Now then. Del Potro is hardly moving at all at the back of the court. Could this be something serious? He already has the service break so this game doesn't matter too much.
This next service game does. Was Del Potro just saving energy?
Del Potro 6-7 (5-7) 6-3 7-6 (7-4) 4-1 Isner*
Ooooh. I assumed the trainer would be for John Isner who was struggling with cramp in that last game but it's not. It's for Juan Martin del Potro.
It seems to be something to do with DelPo's leg. The trainer tells the umpire he'll be back at the next change of ends. There might not be one.
Del Potro 6-7 (5-7) 6-3 7-6 (7-4) 4-1 Isner*
The chance disappears. Is that the end for John Isner? Juan Martin del Potro left the front door unlocked but Isner failed to take the opportunity.
The trainer has been called onto court.
*Del Potro 6-7 (5-7) 6-3 7-6 (7-4) 3-1 Isner
*Groans*
A shanked forehand from Isner goes long. He shapes to whack his racquet off the court before thinking better of it.
Deuce.
*Del Potro 6-7 (5-7) 6-3 7-6 (7-4) 3-1 Isner
And another double fault!
Juan Martin del Potro has gifted John Isner a break point.
*Del Potro 6-7 (5-7) 6-3 7-6 (7-4) 3-1 Isner
John Isner is stretching out his hamstrings at the back of the court. Is he cramping up? Surely DelPo just needs to get the ball in play. He can't do it. Double fault.
Isner is in the game at 30-30.
*Del Potro 6-7 (5-7) 6-3 7-6 (7-4) 3-1 Isner
The crowd appreciate this from John Isner. They roar after he comes through the service game. He's going to have to find a way to break the Del Potro serve though.
Del Potro 6-7 (5-7) 6-3 7-6 (7-4) 3-0 Isner*
Saved! The serve is still going at least for John Isner. The spin is quite something. It's too hot for Del Potro to handle.
Deuce.
Del Potro 6-7 (5-7) 6-3 7-6 (7-4) 3-0 Isner*
"Ooooout," booms a line judge. You can see John Isner deflate.
Two break points to Del Potro.
Del Potro 6-7 (5-7) 6-3 7-6 (7-4) 3-0 Isner*
This could end pretty quickly, I fear.
15-30 on the Isner serve.
The TV pictures are showing slow motion replays of Juan Martin del Potro's forehand and a kid flossing.
One of them is a thing of beauty. I'll let you decide which I mean.