Novak Djokovic sweated it out from behind the baseline to beat Australian John Millman 6-3, 6-4, 6-4 at the US Open on Wednesday and set up a semifinal with Japan's Kei Nishikori.
Djokovic struggled with the humidity at Arthur Ashe Stadium but kept his cool mentally, saving the only break point he faced in the first set and wrapping up the opener in an hour.
"[I was] very tested," Djokovic said. "Almost three hours. It's midnight now. Credit to John for a great battle."
The US Tennis Association said in a statement that Millman was sweating so profusely that the moisture dripping onto court had made the surface too dangerous to play on.
"These night matches the humidity goes through the roof," Millman said. "It is tricky, but it's the same for both people. You're dripping. But that's no excuse or anything. I'd play in a swimming pool if I got to play a quarterfinal every week at a Grand Slam. That would be pretty fun."
In the semifinals, Djokovic will face Japan's Kei Nishikori, who advanced with a 2-6, 6-4, 7-6 (7/5), 4-6, 6-4 victory over Marin Cilic.
Nishikori and countrywoman Naomi Osaka, who also made the semifinals, were heralded by Japanese media. "There is no stopping the Japanese players," screamed the Nikkan Gendai tabloid after the pair became the first from the country to secure semifinal berths in both singles competitions during a Grand Slam.
Osaka next faces American Madison Keys, who beat Carla Suarez Navarro and win 6-4 6-3.