NEW YORK (AP) Andy Murray lost his way, seven consecutive games and, eventually, his riveting five-set U.S. Open quarterfinal against Kei Nishikori after a loud noise from a malfunctioning sound system interrupted a key point, resulting in a do-over.
Whether or not the gong-like sound, and chair umpire Marija Cicak's let ruling, was the reason that Nishikori wound up coming back to win 1-6, 6-4, 4-6, 6-1, 7-5 on Wednesday, it surely will be what's most remembered about the back-and-forth, 4-hour match.
After all, Murray's extended discussions with Cicak and another official about the unusual episode came during a stretch in which he dropped 12 of 14 points.
He went from a lead of two sets to one, plus a break point at 1-all, to ceding the fourth set and trailing 2-0 in the fifth.
''I could have won the match for sure,'' said Murray, the No. 2 seed and 2012 champion at Flushing Meadows.
The No. 6 seed Nishikori reached a Grand Slam semifinal for the first time since he was the U.S. Open runner-up two years ago. He faces No. 3 seed Stan Wawrinka, who ended the resurgent run of 2009 champion Juan Martin del Potro 7-6 (5), 4-6, 6-3, 6-2 in a quarterfinal that finished past 1 a.m. on Thursday. The other men's semifinal Friday is No. 1 Novak Djokovic against No. 10 Gael Monfils.
The last game of two-time major title winner Wawrinka's victory was delayed while the crowd saluted the popular del Potro, who missed the U.S. Open the past two years because of three operations on his left wrist. As fans stood and applauded, del Potro wiped away tears.
Earlier, Murray acknowledged a brief dip in play after the argument over the let but preferred to focus on other reasons for his exit.
''I broke serve enough times,'' Murray said. ''I just didn't hold serve enough. That was the difference.''
But Murray complained about the ruling right away, gave away the next three points to lose the game, then brought it up again with Cicak at the ensuing changeover, saying something similar had happened earlier and play had continued.
''Exactly the same thing,'' Murray exclaimed. ''And I told you.''
He also spoke to a tournament supervisor about it, pleading his case and saying, ''That's not fair.''
That same type of noise came from the speakers again at 4-1 in the fourth set. It also had happened during a women's match Monday night between Ana Konjuh and Agnieszka Radwanska.
The U.S. Tennis Association said Wednesday that a ''digital audio sound processor'' was at fault and would be replaced before the night session.
Despite all the fuss, Murray went ahead 5-4 in the fifth. But he wouldn't take another game. At 5-all, 30-all, Murray double-faulted to set up break point, and Nishikori converted by reaching for a stretch volley winner.
Murray slammed his racket against the net and cursed. Soon enough, his career-best run of reaching seven straight tournament finals was done.
''I would have loved to have gone further,'' Murray said, ''but it wasn't to be today.''
He had won 26 of his previous 27 matches, including a second Wimbledon championship and a second Olympic gold medal, beating Nishikori in straight sets in the semifinals at Rio de Janeiro.
This time, Nishikori came through, helped by a series of effective drop shots and an ability to keep his nerve over the closing three games.
''It was too exciting on the court, but I tried to stay calm,'' he said. ''It was really tough to stay calm. ... There were many ups and downs.''
In the women's quarterfinals, Serena Williams was broken for the first time in the tournament, and lost a set for the first time, too, but eventually got past No. 5 Simona Halep 6-2, 4-6, 6-3. A year ago in the U.S. Open semifinals, Williams' bid for a calendar-year Grand Slam ended with a loss to unseeded Roberta Vinci of Italy.
On Thursday, Williams faces 10th-seeded Karolina Pliskova of the Czech Republic, who reached the first major semifinal of her career by eliminating the 18-year-old Konjuh 6-2, 6-2. The other women's semifinal is No. 2 Angelique Kerber vs. two-time runner-up Caroline Wozniacki.
At 3-all in the second set of Murray vs. Nishikori, rain interrupted play for the second time in the match. The retractable roof atop Ashe was shut during the second, longer shower, and the break of about 20 minutes gave Nishikori's coach, 1989 French Open champion Michael Chang, a chance to run through the concourse to get down to the locker room and consult with his player.
''That helped me a lot to regroup the tactics,'' Nishikori said. ''I (had) to change something to win the match.''
Maybe that made a difference. Murray also thought playing indoors helped Nishikori fare better in his return games. Indeed, Nishikori took that set by breaking in its last game, as Murray slapped a backhand into the net to close a 15-stroke exchange.
The edge went back to Murray late in the third, when he broke to lead 5-4 as Nishikori missed a backhand. Murray roared and punched the air as he went to the sideline. His coach, eight-time major champion Ivan Lendl, did not exactly mirror that celebratory mood, sitting with chin on hand up in the guest box.
Murray served out that set at love and seemed to be in good shape, up two sets to one. At 1-all in the fourth, though, everything changed.
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