Robredo sensed an upset against doubtful Federer

Tommy Robredo suspected he could stun Roger Federer at the US Open because the Swiss master had developed self-doubts, the Spaniard said after the extraordinary upset on Monday.

World number 22 Robredo routed Federer 7-6(3), 6-3, 6-4 at Louis Armstrong Stadium, the 17-times Grand Slam champion failing to convert 14 of 16 break points in his first loss to the Spaniard after 10 successive wins.

"You never know what's going to happen," the gritty 31-year-old Robredo told reporters.

"But obviously Roger when he was number one to the Roger right now, he's not maybe with the same confidence.

"Obviously he's the same player and he plays unbelievable. But I knew if right now I had a little bit more chances, maybe he will have a little bit of doubt."

Robredo, who has played his best Grand Slam tennis on the clay courts at Roland Garros, agreed with Federer's evaluation that he had "self-destructed."

"I always play the same," Robredo said. "So yes, I'm really with him. I think the difference was the break points conversion.

"It's amazing ... For me, Roger for the moment is the best player of all time. And to beat him in the huge stadium like the US Open and in a Grand Slam, a match of five sets, it's like a dream. I am so happy."

A capacity crowd filled Louis Armstrong Stadium in the expectation that Federer would reach the quarter-finals against great rival Rafa Nadal.

But Robredo dominated the first set tiebreak to subdue the spectators who were never to find full voice thereafter as Federer cracked under pressure.

"I wasn't thinking I was going to win," Robredo said.

"I was just going onto the court trying to give my best, and we will see.

"The ball from Roger, it comes like fire. All the time, it's so fast."

Ranked fifth in the world in 2006, Robredo's triumph booked his first quarter-final appearance at Flushing Meadows and marks the crowning moment in a long recovery from a serious hamstring that sent his ranking plummeting to 471 last year.

"I was trying to come back," he said. "I wasn't sure if my leg would be perfect or not. You have your doubts if you're body's going to respond. And ... if you're going to get the confidence back.

"I don't know next week which ranking I'm going to be, but for sure it will be top 20 ... It's an amazing year for me."