Federer stunned by Canas again

Roger Federer [ Images ] suffered a stunning 7-6, 2-6, 7-6 defeat by Guillermo Canas [ Images ] in the Sony Ericsson Open fourth round on Tuesday, the world number one's second loss to the Argentine in successive tournaments.

Second seed Rafael Nadal [ Images ] of Spain and third seeded American Andy Roddick [ Images ] made smooth progress into the final eight.

Nadal swept past Argentine Juan Martin Del Porto 6-0, 6-4 and Roddick advanced with a 7-5, 6-3 win over Spain's David Ferrer.

Canas, who snapped Federer's 41-match winning streak at Indian Wells two weeks ago, battled the Swiss defending champion for two hours 38 minutes in a riveting Stadium court duel that ended when the Argentine sealed victory with a service winner.

Back on the ATP Tour after serving a 15-month doping ban, Canas joins select company, becoming just the fifth player to record back-to-back wins over Federer who lost only two hard court matches all last season.

"I really expecting to win, it was one of those matches I shouldn't have lost," Federer told reporters. "But he's a great competitor. He played well both times and I just couldn't put him away."

Canas, world number 55, was unable to pinpoint the key to his success against a player who has been almost unbeatable since 2004, compiling a sparkling 261-16 record including 35 titles in 51 tournaments.

The 29-year-old Argentine is not without a solid tennis pedigree of his own, however, having been a top 10 player with six career wins before being handed his drug suspension.

"I don't know what it is the key to beat him, I fight for every point and I think for that I beat him," said Canas, who had to qualify for his place in the last two events.

"I think I have luck because I played very well the two matches.

"I think I played great tennis today, for me it's like a dream. To beat two weeks in a row the world number one, it's amazing.

"I don't know what I do, I just know I played very good tennis."

FIRST OPPORTUNITY

After losing the opening set in a tiebreak 7-2, Federer appeared to finally find his rhythm, easily winning the second set and carrying the momentum into the third to break a fading Canas at the first opportunity to go ahead 2-0.

But Canas showed his experience, refusing to buckle under the Federer's pressure and levelling the set at 3-3.

Top seed Federer had several opportunities to regain control but could not break Canas, the Argentine maintaining his perfect record against the Swiss in tiebreaks with a 7-5 success.

"I was in almost total control for almost all the match once I broke back in the first set," said Federer.

"I thought it was a great match, so it was disappointing to lose.

"He dug deep and played well, I was just not in the end very happy with the way things went. I could have won but I didn't do it."

Canas next meets sixth seed Tommy Robredo of Spain in the final eight while Federer will get an early start to his claycourt preparations for the French Open [ Images ].