Roger Federer failed to cope with stifling conditions at the US Open on Monday and suffered a shock 3-6 7-5 7-6(7) 7-6(3) defeat to unseeded Australian John Millman in the last 16.
Second seed Federer, who had not dropped a set in his first three matches, was uncharacteristically sloppy, committing 77 unforced errors and 10 double faults while landing just 49 percent of his first serves.
There was little sign of what was in store for the five-times champion when he took the first set with ease, before world No. 55 Millman turned the tables to win the second then held his nerve through two tiebreaks to secure the victory in three hours and 34 minutes.
While the temperature in New York hovered around 78 Fahrenheit (25C), Federer said high humidity was the problem at Arthur Ashe Stadium.
“I just thought it was very hot tonight,” Federer said. “Was just one of those nights where I felt I couldn’t get air. There was no circulation at all.
“It’s one of the first times it’s happened to me... John was able to deal with it better. He maybe comes from one of the most humid places on earth, Brisbane.
“Some days it’s just not the day where the body can cope with it.”
Millman, who trained with Federer in Switzerland before the grass-court season, was in shock at having beaten one of his idols.
“I’m probably in a little bit of disbelief,” he said. “I have so much respect for Roger and everything he’s done for the game.
“He’s a hero of mine. Today he was definitely not at his best but I’ll take it.”
Unseeded Millman sends Federer crashing out of US Open