Roger Federer knocked out of US Open in fourth round in remarkable defeat against world No 55 John Millman

World No 2 suffers a surprise four-set loss as unheralded Australian Millman records the biggest victory of his career to reach the US Open quarter-finals

Roger Federer’s US Open campaign is over after the world No 2 suffered one of the most remarkable defeats of his career in the early hours of the morning here on Tuesday.

Federer was beaten at a Grand Slam tournament by an opponent ranked outside the world’s top 50 for only the second time since 2003 as 29-year-old John Millman, a journeyman Australian, played the match of his life to win their fourth-round encounter 3-6, 7-5, 7-6, 7-6. On a sweltering night and with the humidity at more than 70 per cent, sweat poured off both men in Arthur Ashe Stadium.

Federer's defeat was comparable only with his second-round loss at Wimbledon in 2012 to Sergiy Stakhovsky, the world No 116. It is only the second time in the last 15 years that he has failed to reach the quarter-finals here.

Perhaps time is finally catching up with the 37-year-old Swiss, who had won all 40 of his previous US Open matches against opponents ranked outside the world’s top 50. He made a remarkable 76 unforced errors in this match – 48 more than Millman – and 10 double faults, including two in a row in the last tie-break.

Millman, the world No 55, had played 10 previous matches against top 10 opponents and never won any of them. He had never previously gone beyond the third round of a Grand Slam tournament but will now face Novak Djokovic, the Wimbledon champion, who wilted in the heat against Portugal’s Joao Sousa before winning 6-3, 6-4, 6-3.

Federer has 98 titles to his name, including 20 at Grand Slam level, while Millman has none, having lost in his only tour-level final in Bucharest earlier this year. The likeable Australian, who is a popular figure on the tour, has had three operations in the last five years which have kept him off the court for long periods and at one stage he started working in business because he feared his playing career might be over.

When Federer raced into a 3-0 lead and went on to take the first set few would have guessed the drama that was to follow. There were signs that he was struggling early in the second set – he kept missing first serves in a marathon second game in which he saved seven break points – but still set the pace and served for the set at 5-4, at which point the whole complexion of the match changed.

Federer made a strong start against Millman as he won the first set. (Getty)

Millman saved two set points when 40-15 down, after which Federer double-faulted on break point. Two games later the Australian broke again to win the set. Federer double-faulted when serving at 40-15 and also lost the next three points as Millman, against all expectations, levelled the match.

Having looked comfortably in control, Federer started to make a succession of mistakes. He played some woeful drop shots, mistimed many of his ground strokes and served without conviction.

There were no breaks of serve in the third set, at the end of which Federer had a set point at 6-5 in the tie-break, only to lose the next three points.

But the 20-time Grand Slam champion looked stumped as he slid towards defeat (Getty)

The world No 2 led again in the fourth set, breaking to lead 4-2, only for Millman to break back immediately. The set went to another tie-break, which started with Millman serving his first double fault of the match.

However, the Australian won the next six points in a row to give himself five match points, Federer having hit two successive double faults at 1-3. Although the Swiss saved the first two match points he hit a forehand long on the third to hand Millman victory as the clock in Arthur Ashe Stadium approached 1am.

The end of the third set saw momentum swing in Millman's favour (AP)

Millman said afterwards that he had felt like “a deer in the headlights” in the early stages and added: “The feet weren't moving. Roger had me on a string. He was manipulating me around the court.”

The Australian said that he had fought hard to stay in the second set and had tried to be more aggressive thereafter. "I've got to control the controllable and the one thing I can control is the fight in me,” he said. “I've always brought the fight up."

Even former president Bill Cllinton couldn't believe what he was seeing (Getty)

Djokovic, who has played 11 fourth-round matches here and won them all, had to survive a difficult patch in his victory over Sousa. For the second time in this tournament the Serb was attended to by the doctor and trainer as he struggled to cope with the heat.

“It's tough,” he said afterwards. “It's not easy to play in these kind of conditions. At the same time, you can't do anything but try to be tough and survive, find a way to win.”

Roger Federer waves goodbye to the crowd after his fourth-round exit (Reuters)

The other quarter-final in a high-quality bottom half of the draw will see Marin Cilic take on Kei Nishikori. Cilic, the 2014 champion, beat David Goffin 7-6, 6-2, 6-4, while Nishikori beat Philipp Kohlschreiber 6-3, 6-2, 7-5.