NEW YORK (AP) -- Kei Nishikori felt like he had jet lag.
That'll happen after playing more than 8 1/2 hours of tennis in two Grand Slam matches separated by about a day and a half. Nishikori did not mind, because he knew he made history. He became the first man from Japan to reach the U.S. Open semifinals in 96 years, outlasting third-seeded Stan Wawrinka of Switzerland 3-6, 7-5, 7-6 (7), 6-7 (5), 6-4 on Wednesday.
''I hope,'' Nishikori said, ''it's big news in Japan.''
The match went 4 hours, 15 minutes, and the 10th-seeded Nishikori managed to shake off any lingering exhaustion from his previous victory, which lasted 4:19 and ended at 2:26 a.m. Tuesday, equaling the latest finish in tournament history.
On Wednesday against the Australian Open champion, Nishikori said, ''I started a little bit tight.''
''But my body was OK,'' he added. ''I don't know how I finished ... but I'm very happy.''
At least now he gets some time to recover. The semifinals are not until Saturday, when Nishikori will face No. 1 Novak Djokovic or No. 8 Andy Murray, who played each other later Wednesday.
''Hopefully I can play 100 percent tennis next round,'' Nishikori said.
The last Japanese semifinalist at the U.S. Open was Ichiya Kumagae in 1918. No man from the country had made it to the final four at any major tournament since Jiri Satoh at Wimbledon in 1933.
Nishikori already was the first Japanese man to be ranked in the ATP's top 10 after climbing to No. 9 in May. He came into the U.S. Open without a lot of proper preparation, because he was sidelined after having a cyst removed from his right foot in early August.
Nishikori, who is coached by 1989 French Open champion Michael Chang, had never eliminated top-10 opponents in consecutive matches at a major tournament. The fourth-round marathon win against No. 5 Milos Raonic put Nishikori in his second career Grand Slam quarterfinal; he lost in that round at the 2012 Australian Open.
Wawrinka had won 15 of his last 16 hard-court Grand Slam matches, a stretch that includes a run to his first major semifinal at last year's U.S. Open and his first Grand Slam championship at the Australian Open.
He also had a lot less wear-and-tear on his body over the past 1 1/2 weeks, thanks in part to getting a walkover when the man he was supposed to play in the third round withdrew with an injury.
But in the end, it was Wawrinka who faltered down the stretch, getting broken to close the match when he slapped a forehand into the net. Nishikori did not really celebrate much, simply looking to the sky as he walked to the net. Chang leaped to his feet and pumped his fists in the stands.
Nishikori credited Chang with helping the mental side of his game and said the coach congratulated him on getting to the semifinals.
''But,'' Nishikori noted, ''he also (said): `It's not done.'''
While the 24-year-old Nishikori put on a brave face before facing Wawrinka, saying he expected to be fine, things did not appear to be OK in the early going. Between points, Nishikori would shake his arms or legs, or flex his hands. During a changeover, he placed a bag of ice on his forehead.
''From outside he looks really dead,'' Wawrinka said, ''but we know on the court he can play.''