I couldn't get air - Federer admits to struggles in US Open heat

Roger Federer is still at the top of his game at the age of 37

The next foe? That could be Roger Federer.

Five-time champion Roger Federer crashed out of the US Open on Monday, beaten in four sets by 55th-ranked Australian John Millman.

Federer started in typical fashion to take the opener 6-3 but Millman didn't wilt, taking the game up to the Swiss to win the next two 7-5, 7-6.

JOHN Millman's stunning victory over Roger Federer in the fourth round of the US Open has thrust the Australian world No.55 into the worldwide spotlight.

7-6 (7/3) defeat to world number 55 Millman was his earliest in NY in five years.

It was also 20-time major victor Federer's first loss against a player outside the top 50 in 41 meetings at the US Open.

With the defeat, the 20-time Grand Slam champion failed to set up a highly-anticipated quarterfinal match-up with his Serbian rival Novak Djokovic, seeded sixth.

The most astonishing thing about Roger Federer's shocking defeat at the U.S. Open is that early on, everything seemed to be going just as expected.

"So I rocked up to Gimcheon and I got there and thought: 'What am I doing?' And it was on my (25th) birthday".

Federer believes the decision to build a roof on Arthur Ashe Stadium contributed to his problems.

There were the five Wimbledons in a row, the five US Opens in a row, the two years where he made the final of every Grand Slam tournament, the most weeks ever as World Number One.yeah, you get the point. Oh, and the answer is, since you are picking second, just take whoever the first pick doesn't! He was up a set and on serve, but the line had been drawn. Before the start of the grass-court season, Federer invited Millman to train with him in Switzerland.

He looked exhausted. He looked weary. This likely wasn't the gratitude Federer was hoping for, but after the match, Federer had nothing but praise for Millman.

But, and hear me out: What if he's not?

Seeing Federer across the net and the bright lights of the largest tennis stadium in the world were all a bit much for the 29-year-old Aussie, who reached his first ATP final in April in Budapest.

A win over Djokovic could propel him even higher than his live ranking of 37. Thousands had stayed well past the midnight hour to witness the genius of Roger Federer in the fourth round of the US Open. It's been 10 years since Fed last won a title in NY and perhaps the slower conditions, high temperatures and, with the new roof on Arthur Ashe Stadium, stagnant air make it harder to win than on the fast courts of a toasty, but not humid, Australian Open and the grass courts at Wimbledon?

What if Federer is feeling the moments and opportunities more as he knows they're dwindling?

Djokovic, who ended a 54-week title drought with his 13th Grand Slam title at Wimbledon, said he was relieved to get past 68th-ranked Sousa in straight sets as temperatures soared again.