Unseeded Australian John Millman has turned the US Open upside down with a colossal fourth-round upset win over 20-times grand slam champion Roger Federer.
In a life-changing performance, Millman left Federer — and fans at Arthur Ashe Stadium — shell-shocked with a 3-6 7-5 7-6 (9-7) 7-6 (7-3) comeback victory to book a quarter-final date with another of tennis's all-time greats, Novak Djokovic.
The victory was Millman's first against a top 10 player. He is also just the second Australian to defeat Federer in a grand slam match and the first since Pat Rafter in 1999.
Since then, nine Australians — including Nick Kyrgios only two days ago, Mark Philippoussis in the 2003 Wimbledon final and Lleyton Hewitt seven times — had fallen prey to Federer in 20 straight grand slam matches over almost 20 years.
But on the very same court on which Federer destroyed Hewitt 6-0 7-6 6-0 in the 2004 US Open final, Millman stared down the greatest player of the professional era to send the world No. 2 crashing to his earliest grand slam defeat in almost four years.
The 29-year-old Queenslander took advantage of an out of sorts Federer who was forced to sweat as the humid New York conditions and an unusually inconsistent serve took their toll.
Millman, ranked 55th in the world entering the match, was as shocked as the New York crowd with the result. Federer had been 40-0 against players ranked outside the top 50 at the US Open.
"A little bit of disbelief, he's been a hero of mine," Millman said after being asked how he felt defeating the greatest tennis player of all time. "He's definitely not at his best, but I'll take it."
He will now play Novak Djokovic in the quarterfinals on Thursday morning (AEST).
The Swiss maestro was caught off guard in the very first game of the match as Australia's last man standing squeezed his way to break point. But a searing ace allowed Federer to survive as he ran away with the first set 6-3.
Millman found some gas in the second set, pinning Federer to the wall in a marathon second game. The 20-time grand slam champion missed 19 of 22 first serve attempts and was forced to defend seven break point opportunities in a 14-minute epic.
Fans noted the amount of sweat on Federer's shirt after the colossal game, with some labelling it is his worst service display in years.
Millman missed the opportunity at an early break and Federer looked to make him pay.
But despite leading 5-3 and then 5-4 40-15, he couldn't put the Aussie away and Millman reeled off three consecutive games to pinch the second set 7-5 and square the match.
The fighting performance continued early in the third as Millman defended a break point to hold serve in the opening game. He worked his way to a 2-1 lead but a love service game from Federer evened out the equation.
Millman hit back and won his seventh of the past nine games to bring it to 3-2. The tug-of-war continued as each player dominated their respective service games to bring the third set to a tense tiebreak.
Before the match, Federer had a word of encouragement for Millman, who has practised with him in Switzefland.
"He's just come to Switzerland to train with me before the grass-court season so we know each other quite well. (He's) a super friendly guy, and I'm very happy for him that he's gotten so far.
"But now I'll try to stop him, so we'll see how it goes."
Millman said the Swiss star was "always someone he looked up to" before their fourth round clash.
Federer could have been forgiven for looking ahead to the quarterfinals, where nemesis Novak Djokovic awaits.
It would be their earliest meeting in a Grand Slam since 2007, when Federer defeated Djokovic to reach the Australian Open quarters.