Lute Olson's doctor said yesterday that the former Arizona men's basketball coach had a stroke within the last year and he advised him to retire.

The comments by Dr. Steven Knope at a news conference called by Olson's family offer the first explanation for Olson's sudden retirement last week, two days after he appeared at the Wildcats' media day. Olson said at the time he was energized and looking forward to his 25th season with Arizona.

Knope said an MRI confirmed the stroke in the frontal part of Olson's brain, which left the Hall of Famer with severe depression and impaired judgment.

Andy Roddick and Juan Martin del Potro boosted their chances of qualifying for the Masters Cup next month by winning their second-round matches in straight sets at the Paris Masters. Third-seeded Novak Djokovic was leading, 6-2, 4-3, against Dmitry Tursunov when the Russian retired with an injured right shoulder, seventh-seeded Roddick beat Feliciano Lopez of Spain, 6-3, 6-4, and No. 9 seed del Potro beat Mario Ancic of Croatia, 6-0, 6-4.

• Roger Federer ended speculation over his Davis Cup plans and announced he will play for Switzerland against the United States March 6-8. The World Group first-round series will be played at a U.S. venue to be chosen by the USTA in the next six weeks.

Erik Compton, who advanced through the first stage of PGA Tour qualifying just five months after his second heart transplant, was given an exemption to play the final tour event of the year. Compton, 28, received one of four sponsor exemptions to the Children's Miracle Network Classic at Disney World Nov. 6-9. It will be his first PGA Tour event in three years.