Roger Federer reacts after losing a point to John Millman during the fourth round of the U.S. Open tennis tournament on Monday in New York. (AP photo)

Looking slow and tired on a sweltering night in Arthur Ashe Stadium, the No. 2-seeded Federer double-faulted 10 times, failed to convert a trio of set points and lost 3-6, 7-5, 7-6 (7), 7-6 (3) in the fourth round to John Millman in a match that began Monday and concluded at nearly 1 a.m. on Tuesday.

To Federer, it was all about the heat and the humidity. With the temperature in the 80s, even with the sun down, and the humidity at about 75 percent, he was unable to summon his usual verve.

“Was just one of those nights where, I guess, I felt I couldn’t get air. There was no circulation at all. I don’t know, for some reason I just struggled in the conditions tonight. It’s one of the first times it’s happened to me,” the 37-year-old Federer said.

It’s only the second time in Federer’s past 14 appearances at the U.S. Open that he’s lost before the quarterfinals. He is, after all, a five-time champion at the tournament.

John Millman returns a shot to Roger Federer during the fourth round of the U.S. Open tennis tournament on Monday in New York. (AP photo)

On the women’s side, Maria Sharapova lost a night match at Flushing Meadows for the first time in her lengthy career, beaten 6-4, 6-3 in a mistake-filled match by No. 30 seed Carla Suarez Navarro of Spain on Monday.