Two-time champion Novak Djokovic ended John Millman's fairytale US Open run on Wednesday, beating the 55th-ranked Australian in straight sets to book a semifinal clash with Kei Nishikori.
The Serbian star, 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 semifinal 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 (7/5), 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 and 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," said Djokovic, who admitted that like many he was surprised to find himself facing Millman, not Federer, across the net.
"But Millman is the kind of a player that makes you miss the balls, makes you win the point, earn the point.
"He doesn't miss a lot himself, so he just runs left, right, gets a lot of balls. Tactically, you've got to find the right balance between being patient but constructive in the point."
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 long, entertaining rallies.
Millman, his clothes soaked, made the unorthodox request to go change after the fourth game of the second set -- Djokovic agreeing.
"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," said Millman.
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.
Against Cilic he labored for four hours and eight 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.
Keys wins
American Madison Keys clinched her second consecutive US Open semifinal berth on Wednesday, using her powerful serve to get an edge on 30th seed Carla Suarez Navarro and win 6-4 6-3.
Keys faces Osaka for a place in the final. Neither have won a grand slam title.
Results: Quarterfinals: Prefix denotes seedings: Men: 21-Kei Nishikori (JPN) bt 7-Marin Cilic (CRO) 2-6, 6-4, 7-6 (7/5), 4-6, 6-4; 6-Novak Djokovic (SRB) bt John Millman (AUS) 6-3, 6-4, 6-4.
Women: 14-Madison Keys (USA) bt 30-Carla Suarez Navarro (ESP) 6-4, 6-3; 20-Naomi Osaka (JPN) bt Lesia Tsurenko (UKR) 6-1, 6-1.