Federer had arrived at the Indian Wells Tennis Garden having won seven consecutive tournaments and was considered an odds-on favorite to break the record of 47 straight matches won by Guillermo Vilas of Argentina 30 years ago.

Canas, an Argentine who got into the tournament as a ''lucky loser'' from qualifying when Xavier Malisse withdrew, played more like a man who once was No. 8 in the world.

Canas went up 6-5 in the first set with a service break and held to close out the set. During the break, Federer removed his shoes and summoned the ATP Tour trainer for the first of two times to attend to an undisclosed problem with his feet.

Federer stayed in the match for a while thereafter. But after Federer had a second visit from the trainer, Canas won the final three games of the set and threw open the championship of this $3.3 million tournament.

Surprisingly, Federer then went out to join Swiss countryman Yves Allegro for a doubles match against David Ferrer and Tommy Robredo of Spain.

Canas returned to the tour in September after serving a 15-month drug suspension. Ranked No. 8 in the world in June 2005, he won his seventh title earlier this year and was ranked 60th when this event got under way. He lost to Alexander Waske in the final round of qualifying, though, and was on the way home until Malisse dropped out.

In a women's third-round match, top-ranked and defending champion Maria Sharapova of Russia stayed on course to repeat with a 7-5, 6-2 win over Nathalie Dechy of France.

Sharapova is playing in her first tournament since early February and is struggling to regain her form. She had four double faults and just one ace, and made 47 unforced errors to go with 24 winners. She has made 97 errors in her two wins, overcoming her miscues by playing well on key points.

''I think that's to be expected,'' she said. ''When you don't compete for that amount of time, it's normal. I definitely feel like these matches are getting the rough stuff (out of the way).

''It's just good to be back on court and being in some tight situations. I miss that after a while.''

Sharapova had been idle since retiring from her semifinal at Tokyo with a left hamstring strain, and she said some of her service inconsistency stems from the injury.

''In Tokyo I struggled with (the serve) a little bit,'' she said. ''Part of it was probably the leg because that's how I injured it. That limited me from serving a lot in practice.''

Sharapova's next opponent will be No. 15 seed Vera Zvonareva, who advanced with a 6-3, 6-3 win over Victoria Azarenko on a day that the top women advanced.

The men's draw, however, was full of upsets.