Two-time champion Novak Djokovic ended John Millman's fairy-tale US Open run on Wednesday, beating the 55th-ranked Australian in straight sets to book a semi-final clash with Kei Nishikori.
The Serb, who ended a 54-week title drought with his 13th grand slam title at Wimbledon, defeated the tenacious Aussie 6-3, 6-4, 6-4 to reach his 11th US Open semi-final in his last 11 appearances.
He lifted the trophy in 2011 and 2015.
Nishikori, the 21st seed, advanced with a 2-6, 6-4, 7-6, 4-6, 6-4 victory over Marin Cilic - the man who beat him in the 2014 final.
Millman, who stunned five-time champion Roger Federer in the fourth round, kept Djokovic running - and was kept running himself - for two hours 49 minutes on another hot, humid night on Arthur Ashe Stadium.
"You survive on the court then thrive with a win," said Djokovic, who converted just four of his 20 break points and made 53 unforced errors before he was finally able to accomplish what Federer couldn't in seeing off Millman.
"Very tested," Djokovic said. "It's midnight now. Credit to John for putting up a great battle. After that kind of win to come out here and fight for three hours - he deserves a round of applause."
It was clear that it could be a long night when the players battled for more than 15 minutes in the sixth game of the opening set, Millman saving four break points.
The Aussie saved another four in the opening game of the second set and as the duel continued both players were clearly feeling the effects of their long, entertaining rallies.
Millman, his clothes soaked, made the unorthodox request to go change after the fourth game of the second set - Djokovic agreeing.
"He was apologising, he felt very sorry that he has to leave the court and change. I said, 'Man, go ahead.'
"I needed that rest," said Djokovic, who finally gained the decisive break in the penultimate game of the final set then served it out at love.
"I gave it a crack," said the 29-year-old Millman, who has battled a litany of injuries in his career.
"I definitely left it all out there today and pulled up a bit short. Novak's a champion. He's played a lot of grand slams and he knows how to win them."
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 stunned then-world No 1 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.
Against Cilic he labored for 4 hours and 8 minutes.
"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."
Unable to match Cilic's level in the opening set and down a break in the second, Nishikori began to turn the tide when he broke Cilic at love to narrow the gap to 4-3.
"Kei started to hit a little bit better. He broke me. He won six games in a row there. From that point on, I felt the match was quite even."