US Open: Federer out, watch out for Djokovic

Roger Federer served poorly. He volleyed poorly. Closed out sets poorly, too. And now he's gone, beaten at the US Open by an opponent ranked outside the top 50 for the first time in his illustrious career.

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 well after midnight on Tuesday morning.

To Federer, it was all about the heat and the humidity. With the temperature in the 30s (Celsius), 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 uncomfortable. Clearly just keep on sweating more and more and more and more as the match goes on. You lose energy as it goes by. But John was able to deal with it better."

It's only the second time in Federer's past 14 appearances at the US Open that he's lost before the quarterfinals. He is, after all, a five-time champion at the tournament, part of his men's-record haul of 20 Grand Slam titles.

"In all honesty, Roger's a hero of mine. I look up to him," said Millman, an Australian who is 29. "I felt a little bit guilty today, because he didn't have his best day, and that's for sure. I know that. I'm very aware he didn't have a great day in the office. Probably, to beat him, I needed him to have an off-day and I needed to have a decent, good day."

Djokovic bids for 3rd US Open

So much for that highly anticipated matchup between Federer and 13-time major champion Novak Djokovic in the quarterfinals. Instead, it'll be the 55th-ranked Millman, who had never made it past the third round at a Slam until last week, taking on No. 6 seed Djokovic.

Hours before, Djokovic left the court for a medical timeout — the second time during the tournament he's sought help from a doctor because of harsh weather — during what would become an otherwise straightforward 6-3, 6-4, 6-3 victory over 68th-ranked Joao Sousa of Portugal.

"I'm not 21 anymore. That was 10 years ago. I still don't feel old. But at the same time, there is a little biological clock that is not really working in your favor," Djokovic said. "Sometimes, you just have to survive."

He reached the quarterfinals for an 11th consecutive appearance in New York as he bids for a third US Open championship and 14th Grand Slam trophy.

The other quarterfinal on the bottom half of the draw will be a rematch of the 2014 US Open final: No. 7 Marin Cilic against No. 21 Kei Nishikori.