Kei Nishikori reached the US Open semi-finals on Wednesday, holding on for a 2-6, 6-4, 7-6 (7/5), 4-6, 6-4 victory over Marin Cilic — the man who beat him in the 2014 final.

Japan’s Nishikori, who missed last year’s US Open after a season-ending wrist injury, joined compatriot Naomi Osaka in reaching the semis — the first time that a Japanese man and woman have reached the last four in the same Grand Slam.

Nishikori, the 21st seed, will take on either 13-time Grand Slam champion Novak Djokovic or 55th-ranked Australian John Millman for a place in the final.

Nishikori stunned then-world number one Djokovic in the semi-finals in 2014 to become the first man from an Asian country to reach the championship match of a Major.

But he hasn’t returned to a Grand Slam final since, falling in the US Open semis in 2016.

Ranked as high as fourth in the world in 2015, Nishikori made a cautious return to competition early this year, finally finding enough confidence and consistency to put together a quarter-final run at Wimbledon. Against Cilic he labored for 4 hours and 8 minutes.

“It was really tough, especially in the end I was up 3-2 and he came back — I don’t know why but it’s always a battle with Marin,” said Nishikori, who stretched his career record over the seventh-seeded Croatian to 9-6.

Nishikori appeared to be in control of the fifth set with a break for a 3-1 lead.

He had two game points for a 5-2 lead but a double fault and a backhand wide opened the door for Cilic, who stormed through, shouting “Got it!” when he secured the break to narrow the gap to 4-3.

But Nishikori broke Cilic in the final game, capturing the match with a blistering service return.

“I try to fight every point,” said Nishikori, who boasts an impressive record in decisive sets.

“Especially in the end I really focus on every point,” he said but added: “I wish I don’t go to five sets every time.”

The night session on Arthur Ashe Stadium featured Wimbledon champion Djokovic, the sixth seed, taking on the 55th-ranked Australian Millman who stunned 20-time Grand Slam champion Roger Federer in the fourth round.

The Serbian star has continued to shine since ending a 54-week title drought with his 13th Grand Slam title at Wimbledon, warming up for the US Open with a victory at the Cincinnati Masters.

Millman, a 29-year-old whose career has been blighted by a string of injuries and three surgeries, wasn’t the man he was expecting to see across the net at this stage.

But the unheralded player from Down Under took full advantage of Federer’s off night to become the first Australian quarter-finalist in New York since Lleyton Hewitt in 2006.

If he could get past Djokovic, Millman would become the first Aussie man to reach a Slam semi-final since Hewitt at the 2005 US Open.

The odds aren’t good. Djokovic is playing in his 11th US Open quarter-final in his last 11 appearances.

The two-time champion is 10-0 in last-eight matches — in which he has never before faced a player ranked outside of the top 25.

In his only prior clash with Millman, Djokovic gave up just three games in a victory at Queen’s Club this year.

“I’ll have to improve a lot on the last time I played him,” Millman admitted. “But why not?”