NEW YORK - Kei Nishikori became the first Japanese man for almost a century to reach the US Open semi-finals on Wednesday after securing an epic 3-6, 7-5, 7-6 (9/7), 6-7 (5/7), 6-4 win over Stan Wawrinka.
Nishikori, the 24-year-old 10th seed, triumphed in 4 hours 15 minutes, his second marathon clash after needing 4 hours 19 minutes to get past Milos Raonic in the previous round.
Nishikori will face either world number one Novak Djokovic or Andy Murray, both former champions, on Saturday for a place in Monday's championship match.
Ichiya Kumagae was the last Japanese man to reach the semi-finals of the US Championships in 1918.
Nishikori, whose match against Raonic ended at a record-equalling 2:26am on Tuesday, was stunned by his win over the third seeded Wawrinka, the Australian Open champion who had won the pair's two other meetings without dropping a set.
"I was tight at the start but my body was OK. I felt more confident after the first set," said the 24-year-old, who will be playing in his first Grand Slam semi-final having made the quarter-finals in Australia in 2012.
"It feels amazing. I am playing well and I hope to play at 100 per cent in the semi-finals." Nishikori stands at 1-1 against Djokovic and trails Murray 3-0 having lost to the Briton in the quarter-finals in straight sets in Melbourne two years ago.
Wawrinka, bidding for a second successive semi-final place, swept through the first set on the back of a break in the second game with Nishikori managing just two winners as the hangover from his early Tuesday morning heroics appeared to affect him.
But he was transformed in the second set, forcing the Swiss to save three break points in the eighth game before levelling the quarter-final in the 12th when Wawrinka served up his fourth double fault of the afternoon.
In a gruelling third set, Nishikori stretched to a 5-2 lead but after squandering a set point in the ninth game, the tiebreak was required to separate them.
Wawrinka, 29, saved another set point with a nerveless passing shot, then the Japanese performed the same escape act with a backhand down the line.
But Nishikori came through the breaker much to the delight of watching coach Michael Chang.
The 10th seed needed a medical timeout after three games of the fourth set to treat a problem with his right toe and the set was as tight as his strapping as Wawrinka went on to take the tiebreaker and make the tie a one-set shootout.
Wawrinka missed a break point in the fifth game of the final set and he eventually cracked in the 10th when Nishikori took victory on a Swiss netted forehand.
The world number four had served up 18 aces but committed 78 unforced errors and managed to convert just two of 10 break point opportunities.
World number one and Wimbledon champion Djokovic takes a 12-8 career record over Murray into their last-eight clash between the two former champions who have been rivals since they were 13 years old.
Top seed Djokovic, the 2011 champion, has made the final in the last four years while Murray was the champion in 2012 when he beat Djokovic in a 4hr 54min record equalling marathon final.
A win for Djokovic, who has yet to drop a set at the tournament this year, would take him to an eighth US Open semi-final, the same as Roger Federer and Ivan Lendl but four behind the record of Jimmy Connors.
The remaining quarter-finals will take place on Thursday with sixth seeded Czech Tomas Berdych, a semi-finalist in 2012, taking a 5-3 record into his clash against 14th seeded Croatian, Marin Cilic.
But Cilic, who missed last year's tournament while serving a doping ban, won their most recent encounter in straight sets in the third round at Wimbledon.
Five-time champion Roger Federer faces French entertainer Gael Monfils who has reached the quarter-finals for the second time, four years after his first.