Andy Murray frustrated after US Open exit

Murray was beaten 1-6 6-4 4-6 6-1 7-5 by the Japanese, who capitalised on the world number two's loss of focus after a series of unusual circumstances in Arthur Ashe Stadium.

First a rain delay, lasting 22 minutes while the roof was closed, turned momentum in Nishikori's favour and then a loud noise from the stadium's malfunctioning sound system derailed Murray's charge.

The second incident was more costly as the noise came during a Murray break point early in the fourth set and umpire Marija Cicak ordered the point to be replayed.

Murray's anger intensified when Nishikori held and after complaining to both Cicak and tournament referee Wayne McKewen, he proceeded to lose the next seven games in a row.

"They stopped the point and I was just curious why that was and that was it," Murray said.

"(Referee) Wayne McKewen told me that it happened four times during the match that the speakers had gone off like that.

"I had only heard it one time before, which was on set point in the second set. That was it.

"Did it affect me? Definitely I would say to 4-1. I didn't play a good game after I got out of the change of ends and then he held pretty comfortably the next game.

"But after that I don't think so. There was a lot of time after then. I lost my serve a couple of times from positions that when I was up in the game. That was the difference."

Murray's defeat means Flushing Meadows will feature the first grand slam final of the year without the British number one.

He arrived in New York on the back of seven consecutive tournament finals, including summer triumphs at Wimbledon and the Olympics, but insisted fatigue was not a factor.

The three-time major champion twice broke back in a thrilling decider but was unable to escape a third time.

"I felt alright today," Murray said. "Kei has played a lot of tennis as well over the last few months for sure.

"But this slam in particular I think for all of the players, especially the ones, that have done well over the summer period on the hard courts, it's a tough one.

"Kei will be feeling it, as well as a lot of the players. I don't think that had an impact on the match today."

Nishikori, runner-up here in 2014, goes through to his second grand slam semi-final, where he will face either Stan Wawrinka or Juan Martin del Potro.

The 26-year-old was in no doubt the right decision was made to replay the point interrupted by noise.

"Definitely. My concentration went off," Nishikori said. "I don't know what's the reason for the noise, but for sure they have to stop that."

Nishikori also admitted he took advantage of the rain delay in the second set, as it allowed him to re-think his tactics.

"It was definitely my mistakes that lost the first set. I was missing too much," Nishikori said.

"We talk a lot of things during the rain delay and, yeah, I tried to change something. It worked well. For sure it helped today's game."