Federer vows to fight on

New York - After crashing out in the fourth round of the US Open against an opponent who had never before beaten him, 17-time Grand Slam winner Roger Federer shrugged off any notion he might quit after Monday's loss.

"I've definitely got to go back to work and come back stronger, get rid of this loss now as quick as I can, forget about it, because that's not how I want to play from here on," Federer said.

"I want to play better. I know I can."

Federer fell to Spanish 19th seed Tommy Robredo 7-6 (7/3), 6-3, 6-4, dooming hopes for a potential quarter-final match with 12-time Grand Slam winner Rafael Nadal, what would have been their first meeting on the New York hardcourts.

The 32-year-old Swiss star won only two of 16 break-point chances and while he smacked 45 winners, including five aces, he also made 43 unforced errors, an underwhelming effort from a player who once dominated the sport.

"The story of my life - when I lose, people are shellshocked to see me play this way. If I win, it's the best thing," Federer said.

"I can see that. But there's no doubt about it, I'm trying hard out there trying to make it work.

"Sometimes it just doesn't happen."

That shattered aura of invincibility gives opponents like Robredo, who says that "Roger for the moment is the best player of all times," the idea they can defeat Federer now.

"Roger, when he was number one, compared to the Roger right now, he's not maybe with the same confidence," said Robredo who claimed his first ever win over the Swiss in 10 meetings.

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

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 and the first year since 2003 that he failed to reach the last eight at the US Open.

"It has been a difficult last three months," Federer said. "My consistency is just not quite there yet. Maybe on a daily basis, set-by-set or point-by-point basis, maybe that's something that has been difficult for me, so maybe that was one of the reasons I lost."

Federer takes some confidence from capturing his lone title of the year at Halle in June and runs to the Hamburg semi-finals and Cincinnati quarter-finals.

"I showed it the last few weeks, that there is that (higher) level, so today was pretty frustrating," Federer said.

"Important for me, first and foremost, is that I move better, that I play better. My problem is in training, not actually playing matches right now."

The five-time US Open champion has no plans on making major changes right away to his training regimen or match strategy, but searching for ways to make his game better, Federer said, promised to be an enticing challenge.

"I haven't thought of it right away," he said. "Nothing goes past the hard work. I'll make sure I'll put the work in. Once I decide what that is, I'll believe in it and go after it.

"In some ways, as a player, you're always excited about that prospect because there's always something to look forward to, even in a big disappointment like the match today."

Federer's match was hit by a four-hour rain delay and moved from the showpiece Arthur Ashe Stadium to Louis Armstrong Stadium, where he had not played since 2006.

But those were excuses he shrugged off.

"I've waited for so many matches throughout my career. That's definitely the last excuse you could find," Federer said.

"I thought it was going to be a great atmosphere, that I could take advantage of maybe the fact that people were really going to get behind me.

"But unfortunately I didn't show the game that they could really get into it and excited about. That's how it goes sometimes."

Talk of a potential match-up with Nadal was no distraction either, Federer said.

"I didn't think of that," he said. "I've been too often in this situation. I was fighting with other things in my match. Not thinking too far ahead of myself, especially the level I was playing at."