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
Saj Chowdhury and Matthew Henry
*Del Potro 6-7 (5-7) 0-0 Isner
Well that tie-break from big John Isner was quite something. Pretty much unplayable. Saj has nipped off for a breather. Matt Henry here to take you through this next set.
Del Potro will start it off.
Del Potro 6-7 (5-7) Isner
Ace.
Isner takes the first set.
What a serve!
Del Potro 6-6 (5-6) Isner
The gutsy Del Potro wins the next point on his serve by finding the corner.
And the next with an ace down the T.
Isner to finish the job?
Del Potro 6-6 (3-6) Isner
Isner smacks down an eighth ace.
5-3 Isner.
He moves to set-point with another big serve.
Del Potro must win these points.
Del Potro 6-6 (3-4) Isner
Del Potro pulls out the serve and volley tactic.
3-3.
The players change ends, and have a swig of liquid en route.
Isner rushes to the net forcing Del Potro to look for a winner.
He goes wide.
Mini-break!
Del Potro 6-6 (2-3) Isner
Isner serves out wide, Del Potro returns but the American reads it to fire down a forehand winner.
An ace follows - 139mph. The fastest serve of the match.
Back to you Delpo.
Del Potro 6-6 (2-1) Isner
The American then goes wide when perhaps he should have come to the net to put the pressure on his opponent.
1-1.
A great serve forces an error from Isner.
2-1 Del Potro.
Del Potro 6-6 (0-1) Isner
Isner comes to the net and smashes down a winner to win the first point on his serve.
Del Potro 6-6 Isner*
30-15.
40-15.
Del Potro loses sight of the ball as the frame of his racquet comes in contact with the ball.
40-30.
A big serve brings up game and a tie-break.
Isner in a tie-break? Well, I never.
Del Potro 5-6 Isner*
Isner tries a change of tactic with sliced returns from the back. They have no effect as Del Potro produces another wonderful forehand winner.
The American then goes long.
30-0.
Some of the crowd sing, "Delpo!".
Their lad's doing well.
*Del Potro 5-6 Isner
Break point!!!!
Isner makes another error.
The American's kick serve forces Del Potro to stretch to reach the ball. He returns but Isner is there to slap down the winner.
Deuce.
Advantage.
Then Isner saves by coming to the net and playing a deft cross-court volley.
*Del Potro 5-5 Isner
Isner produces his 10th unforced error.
15-15.
More pressure on the home favourite as his forehand from Del Potro's aggressive return lands wide.
15-30.
Out of trouble with a huge serve.
Del Potro 5-5 Isner*
The world number three powers down an angled serve which is returned, but the Argentine is in the right place near the net to put away the winner.
Game.
Del Potro 5-4 Isner*
0-15.
But Del Potro produces a great second serve for 15s each.
Isner then goes long as he pounces of a return, before a Delpo smash at the net brings up 40-15.
*denotes next server
*Del Potro 4-5 Isner
30-30.
Ace, but Delpo challenges. He loses the challenge by an inch.
Another ace.
40-30.
Isner repeats the trick with another which is measured at 134mph.
*Del Potro 4-4 Isner
Isner loses the first point on his serve as he goes wide with a forehand.
The next forehand finds its target, with a bit of help from a clip off the net.
15-15.
Del Potro then smacks, with pace, a double-handed backhand winner. Isner was stcuk in the mud.
15-30.
Hmmm...
Del Potro 4-4 Isner*
30-15.
Isner looks disgusted with himself after he loses the next point with a long looping return.
His next return finds the net.
It's going to serve.
Del Potro 4-3 Isner*
Slight concern for Isner is that he's only managed 45% of first serves in.
We'll see how that develops.
Del Potro on serve and wins the first point as Isner loops long.
15-0.
*Del Potro 4-3 Isner
40-30.
Del Potro goes long.
Game.
The players retreat to their chairs and apply the ice sausages.
*Del Potro 3-3 Isner
Isner makes his fifth error.
It's 30-30.
Yikes!