NEW YORK: Roger Federer suffered a stunning upset in the fourth round of the US Open, the 17-time Grand Slam champion falling to Spanish 19th seed Tommy Robredo 7-6 (7/3), 6-3, 6-4 in a last-16 match Monday.

Federer's failure came on the heels of a shock second-round Wimbledon exit and thwarted a potential quarter-final showdown with 12-time Grand Slam winner Rafael Nadal, in what would have been their first duel on the New York hardcourts.

Instead, it will be Robredo, in his first US Open quarter-final, against Nadal, who beat Germany's 22nd-seeded Philipp Kohlschreiber.

Robredo, who had lost his 10 prior matches against the Swiss star, suffered seven prior fourth-round US Open defeats and matched his best Grand Slam performance by finally breaking through.

“I'm delighted. Today the difference is I won the break points and he did not,” said 31-year-old Robredo. “It was a really, really tough night and I am so happy. It was really a great experience.”

Federer won only two of 16 break-point chances. He hit 45 winners but also made 43 unforced errors and managed only five aces while Robredo hit 70 per cent of his first serves and won four of his seven break chances.

In taking as many sets off Federer as he had in their 10 prior matches combined, Robredo also raised questions about the future of the 32-year-old former world number one, who had not missed the US Open quarter-finals since a fourth-round exit in 2003.

Federer had made 36 consecutive Grand Slam quarter-final appearances before being upset by Ukrainian Sergiy Stakhovsky in the second round at Wimbledon, having not departed a major before the last eight since the 2004 French Open.

This was the first year since 2002 that Federer has not made a Grand Slam final.

It was the first time Federer has missed the last-eight in consecutive Slams since the 2003 Australian and French Opens, just before he won his first major crown at Wimbledon later that same year.

Federer, whose seventh seeding at the US Open was his lowest at a Grand Slam event since 2002, failed to match the career record of 41 Slam quarter-finals by retired US star Jimmy Connors.

A rain delay of more than four hours pushed Federer's match from Arthur Ashe Stadium to Louis Armstrong Stadium, marking the first time since a 2006 triumph over Frenchman Marc Gicquel that Federer had played at the secondary court.

Federer's only defeat in eight prior Armstrong appearances came when he lost to Spain's Juan Carlos Ferrero in the third round in 2000 in US first US Open.

“Amazing, eh,” Robredo said. “I beat the best guy of all times in a great stadium like this where he loves to play.”

Federer had made eight career comebacks to win after dropping the first two sets but he failed on five break points in the fourth game of the third set, which Robredo held to reach 2-2, and there was a sense a comeback chance had been squandered.

Robredo broke Federer at love in the seventh game for a 4-3 edge and they held to set up Robredo serving for the match in the 10th game, fans chanting, “Let's Go Roger” in vain hopes of willing the wilting once-king to a rally for the ages, only to watch as Robredo held again to win in two hours and 24 minutes.

Robredo took advantage of his fourth break point in the opening game of the match but handed Federer a break to 2-2 when he swatted a forehand beyond the baseline.

Federer netted a volley to hand Robredo a 5-4 lead but the Spaniard could not claim the set on his serve, Federer equalizing when Robredo swatted a forehand long on the way to a tie-breaker.

Robredo won the final four points to take the first set, the last of them on a 120-mph ace, and seized command by breaking Federer at love in the eighth game of the second set for a 5-3 edge.

Robredo then served out for the set, taking it when Federer netted a backhand. Federer missed on all six break-point chances he managed in the set.

Meanwhile, world number two Rafael Nadal avoided the same fate which befell Roger Federer to reach the US Open quarter-finals with a 6-7 (4/7), 6-4, 6-3, 6-1 win over German 22nd seed Philipp Kohlschreiber.

Nadal, the 2010 champion in New York, stayed on course for a 13th Grand Slam title and will next face fellow Spaniard Tommy Robredo, who shocked 17-time major winner Federer 7-6 (7/3), 6-3, 6-4.

Second seed Nadal fired 48 winners and took his year record to 57 wins against just three defeats and his perfect hardcourt form to 19 wins.

He also preserved his record this year at the tournament of not having dropped serve, although he had a rocky start to the evening against the big-hitting Kohlschreiber, who finished with 49 winners but 47 unforced errors.

Nadal certainly had the 29-year-old German under the cosh throughout their last-16 tie, carving out 21 break points, converting five.

“It was very tough tonight with the humid conditions, I was sweating too much,” said Nadal after three hours and 12 minutes on court.

“I had chances in the first set but couldn't take them. I feel lucky to be through as it was physically tough. “But as the match went on I felt more comfortable on my serve.”Next up for Nadal is Robredo against whom he has a 6-0 record.

“He's playing great and he has had similar circumstances like me in coming back from injury,” said Nadal.

“He has come back and is having an amazing tournament. He has beaten Federer so he will bring that confidence into the match.”

As news of Federer's stunning defeat to Robredo on the neighboring Louis Armstrong Court spread around the Arthur Ashe Stadium, Kohlschreiber sensed his chance of a shock and took the first set on a tie-breaker.

But Nadal eventually broke through for a 4-3 lead in the second set to level up the encounter.

The 27-year-old Spaniard kept up the barrage at the start of the third with Kohlschreiber fending off eight break points in the opening game before Nadal achieved the break in the third game.

He back it up with another break in the ninth as he sighted the quarter-finals.

Kohlschreiber, who had only beaten the world number two once in 10 meetings before Monday, was wilting and dumped an easy smash into the net in the first game of the fourth set which would have given him an early break.

Nadal made him pay as he raced away with victory.