Canas announces retirement

KEY BISCAYNE, Fla. -- Guillermo Canas, once a nemesis to Roger Federer, has announced his retirement from tennis.

The 32-year-old Canas said Friday he decided to retire rather than undergo a fifth operation on his right wrist. He has been battling pain in the wrist for more than a year and hasn't played in a tournament since July.

Canas made the announcement at the Sony Ericsson Open, where he's remembered for upsetting the top-ranked Federer in March 2007. Canas also won when they met at Indian Wells earlier that same month, ending Federer's 41-match winning streak.

"I beat the most talented player in the world," the Argentine said. "For me it was unbelievable. And then to do it again 10 days later was like a dream for me."