See you back here tomorrow for some women's semi-final action.
That break down thusly:
Serena Williams or Simona Halep v Karolina Pliskova
and
Caroline Wozniacki v Angelique Kerber
Keep an eye on the website for live scores from Stan Wawrinka v Juan Martin del Potro.
Laters.
Post update
Nishikori 1-6 6-4 4-6 6-1 7-5 Murray
Some quotes from Andy Murray's news conference. He is immediately asked about the gong noise from the speakers, which disrupted him when he had a break point in the fourth set.
"When we stopped the point at break point at the beginning of the fourth set it was the fourth time it had happened in the match and the first time we had stopped the point," says Murray.
"I didn't play a good game after I got up from the change of ends, but after that there was a lot of time and I had a lot of game points in the 4-1 game. I lost my serve a couple of times when I was up in the game. That was the difference.
"It is different serving under the roof. It slows the conditions down and becomes easier to return. You have delays in matches and that is not good for television. You want to watch the match without any breaks, but you want to complete as many matches as possible outdoors.
"Under the roof he was able to dictate more of the points and was playing closer to the baseline than me."
Post update
Murray out of US Open
Andy Murray has been speaking to the media after his defeat.
He is fairly philosophical and it sounds like he feels the closing of the roof rather than the backfiring speakers were the bigger factor in his defeat.
Full quotes to come.
Semi-final line-up
So this is how your semi-final line-up is looking:
Novak Djokovic v Gael Monfils
Stan Wawrinka or Juan Martin del Potro v Kei Nishikori
Thanks to a withdrawal and two retirements, Novak Djokovic has spent just six hours and 26 minutes on court across his five matches.
By contrast, Nishikori was on court almost four hours tonight alone.
'Strategically smart'
Nishikori 1-6 6-4 4-6 6-1 7-5 Murray
Gong!
Andy Murray was two sets to one up and was halfway through a point which, had he won, would have moved him a break up in the fourth, when a hugh gonging noise forced the umpire to replay the point.
Murray failed to break when play resumed and was broken himself in the very next game.
So what was the cause?
The United States Tennis Association have released a statement blaming a malfunction in the "digital audio sound processors" in the Arthur Ashe arena.
I'm sure Andy Murray will have some "feedback" for them on that one.
Post update
Post update
Nishikori 1-6 6-4 4-6 6-1 7-5 Murray
Serve stats
Andy Murray managed only a 55% hit-rate with his first serve and won only 39% of points behind his second serve.
That was the spoiler that prevented the world number two taking flight.
Nishikori was reading his second serve like the Gruffalo by the end of the match.
"It was too exciting on the court"
Getty ImagesCopyright: Getty Images
Kei Nishikori speaking on court: "It was too exciting on the court, but I tried to stay calm. In the beginning I didn't start well, he has a great return, but I finished well. The rain delay helped me to change tactics. I tried to hit a few more drop-shots than usual today and it worked really well today.
"I have great memories of this place and this is a great chance for me in the semi-finals."
Game, set and match
Nishikori 1-6 6-4 4-6 6-1 7-5 Murray
Getty ImagesCopyright: Getty Images
Kei Nishikori throws his head back and puffs out his cheeks.
Andy Murray looks wiped. A supreme athlete in body, but a jaded everyman behind the eyes.
Two match points Nishikori
*Nishikori 1-6 6-4 4-6 6-1 6-5 Murray
Andy Murray bets the house on a big return. And pumps wide. 40-15 Nishikori and two match points.
Post update
*Nishikori 1-6 6-4 4-6 6-1 6-5 Murray
Kei Nishikori steadies the ship. 15-15.
Another big serve. 30-15 to the Japanese.
Post update
*Nishikori 1-6 6-4 4-6 6-1 6-5 Murray
Double fault first point.
Murray up 0-15. Nishikori's coaches turning psychologists in their box.
Nishikori breaks
*Nishikori 1-6 6-4 4-6 6-1 6-5 Murray
APCopyright: AP
Nishikori drop-shots...Murray scampers.. he prises it off the floor...Nishikori flashes out a racquet...ball hits strings and drops...IN!
Murray chops at the net cord in frustration.
Nishikori serves for the match next...
Break point Nishikori
Nishikori 1-6 6-4 4-6 6-1 5-5 *Murray
Andy Murray sends a forehand streaking wide to spark a bout of gripping and grimacing from the Scot.
Fifteen-all.
The murmur and burble of the crowd is in Murray's ear as he prepares to serve. The umpire issues a warning to the public.
Murray duffs into the net. Nishikori with 15-30.
Murray gobbles up a helpful netcord for 30-30.
Double fault! Break point Nishikori.
Post update
Nishikori 1-6 6-4 4-6 6-1 5-5 *Murray
Jeff Tarango
Former professional tennis player on BBC Radio 5 live
This is where you have to erase all pain from the brain. You can't think how much your legs hurt or how sore your neck is. It is all desire from now on.
Nishikori holds
Nishikori 1-6 6-4 4-6 6-1 5-5 *Murray
APCopyright: AP
I feared for Nishikori's psyche as he fussily picked fluff of a ball before his opening serve. I needn't.
Andy Murray drifts successive returns long over the baseline to hand Kei Nishikori a pass straight to 30-0.
A dreamy lob over the top of the Scot brings up 40-0.
And Nishikori's brute force seals the game on the next.
Get Involved #bbctennis
Henry Monk: I think it shows why Murray is a grand slam winner by showing grit to get himself to 5-4 first.
Live Reporting
Mike Henson
All times stated are UK
Get involved
Getty ImagesCopyright: Getty Images 
Getty ImagesCopyright: Getty Images 
APCopyright: AP 
APCopyright: AP
Latest PostBye for now
Andy Murray is off for some well-earned rest.
I'm off for a sarnie.
See you back here tomorrow for some women's semi-final action.
That break down thusly:
Serena Williams or Simona Halep v Karolina Pliskova
and
Caroline Wozniacki v Angelique Kerber
Keep an eye on the website for live scores from Stan Wawrinka v Juan Martin del Potro.
Laters.
Post update
Nishikori 1-6 6-4 4-6 6-1 7-5 Murray
Some quotes from Andy Murray's news conference. He is immediately asked about the gong noise from the speakers, which disrupted him when he had a break point in the fourth set.
"When we stopped the point at break point at the beginning of the fourth set it was the fourth time it had happened in the match and the first time we had stopped the point," says Murray.
"I didn't play a good game after I got up from the change of ends, but after that there was a lot of time and I had a lot of game points in the 4-1 game. I lost my serve a couple of times when I was up in the game. That was the difference.
"It is different serving under the roof. It slows the conditions down and becomes easier to return. You have delays in matches and that is not good for television. You want to watch the match without any breaks, but you want to complete as many matches as possible outdoors.
"Under the roof he was able to dictate more of the points and was playing closer to the baseline than me."
Post update
Murray out of US Open
Andy Murray has been speaking to the media after his defeat.
He is fairly philosophical and it sounds like he feels the closing of the roof rather than the backfiring speakers were the bigger factor in his defeat.
Full quotes to come.
Semi-final line-up
So this is how your semi-final line-up is looking:
Novak Djokovic v Gael Monfils
Stan Wawrinka or Juan Martin del Potro v Kei Nishikori
Thanks to a withdrawal and two retirements, Novak Djokovic has spent just six hours and 26 minutes on court across his five matches.
By contrast, Nishikori was on court almost four hours tonight alone.
'Strategically smart'
Nishikori 1-6 6-4 4-6 6-1 7-5 Murray
Gong!
Andy Murray was two sets to one up and was halfway through a point which, had he won, would have moved him a break up in the fourth, when a hugh gonging noise forced the umpire to replay the point.
Murray failed to break when play resumed and was broken himself in the very next game.
So what was the cause?
The United States Tennis Association have released a statement blaming a malfunction in the "digital audio sound processors" in the Arthur Ashe arena.
I'm sure Andy Murray will have some "feedback" for them on that one.
Post update
Post update
Nishikori 1-6 6-4 4-6 6-1 7-5 Murray
Serve stats
Andy Murray managed only a 55% hit-rate with his first serve and won only 39% of points behind his second serve.
That was the spoiler that prevented the world number two taking flight.
Nishikori was reading his second serve like the Gruffalo by the end of the match.
"It was too exciting on the court"
Kei Nishikori speaking on court: "It was too exciting on the court, but I tried to stay calm. In the beginning I didn't start well, he has a great return, but I finished well. The rain delay helped me to change tactics. I tried to hit a few more drop-shots than usual today and it worked really well today.
"I have great memories of this place and this is a great chance for me in the semi-finals."
Game, set and match
Nishikori 1-6 6-4 4-6 6-1 7-5 Murray
Kei Nishikori throws his head back and puffs out his cheeks.
Andy Murray looks wiped. A supreme athlete in body, but a jaded everyman behind the eyes.
Two match points Nishikori
*Nishikori 1-6 6-4 4-6 6-1 6-5 Murray
Andy Murray bets the house on a big return. And pumps wide. 40-15 Nishikori and two match points.
Post update
*Nishikori 1-6 6-4 4-6 6-1 6-5 Murray
Kei Nishikori steadies the ship. 15-15.
Another big serve. 30-15 to the Japanese.
Post update
*Nishikori 1-6 6-4 4-6 6-1 6-5 Murray
Double fault first point.
Murray up 0-15. Nishikori's coaches turning psychologists in their box.
Nishikori breaks
*Nishikori 1-6 6-4 4-6 6-1 6-5 Murray
Nishikori drop-shots...Murray scampers.. he prises it off the floor...Nishikori flashes out a racquet...ball hits strings and drops...IN!
Murray chops at the net cord in frustration.
Nishikori serves for the match next...
Break point Nishikori
Nishikori 1-6 6-4 4-6 6-1 5-5 *Murray
Andy Murray sends a forehand streaking wide to spark a bout of gripping and grimacing from the Scot.
Fifteen-all.
The murmur and burble of the crowd is in Murray's ear as he prepares to serve. The umpire issues a warning to the public.
Murray duffs into the net. Nishikori with 15-30.
Murray gobbles up a helpful netcord for 30-30.
Double fault! Break point Nishikori.
Post update
Nishikori 1-6 6-4 4-6 6-1 5-5 *Murray
Jeff Tarango
Former professional tennis player on BBC Radio 5 live
This is where you have to erase all pain from the brain. You can't think how much your legs hurt or how sore your neck is. It is all desire from now on.
Nishikori holds
Nishikori 1-6 6-4 4-6 6-1 5-5 *Murray
I feared for Nishikori's psyche as he fussily picked fluff of a ball before his opening serve. I needn't.
Andy Murray drifts successive returns long over the baseline to hand Kei Nishikori a pass straight to 30-0.
A dreamy lob over the top of the Scot brings up 40-0.
And Nishikori's brute force seals the game on the next.
Get Involved #bbctennis
Henry Monk: I think it shows why Murray is a grand slam winner by showing grit to get himself to 5-4 first.