KEY BISCAYNE, Fla. — Andy Roddick missed his chance on Sunday to play Dwyane Wade in H-O-R-S-E.

Roddick was too busy trying to beat Dmitry Tursunov at tennis.

Already off to the fastest start of his career this year, Roddick reached the fourth round at the Sony Ericsson Open by defeating Tursunov 7-6 (9), 6-2.

His 25th victory this year — most on the ATP Tour — was considerable consolation. It didn’t come easily: The No. 5-seeded Roddick erased two set points in the tiebreaker, one with an ace and the second when Tursunov netted a forehand, and won the final three points in a stressful 75-minute first set.

Roddick lost his temper early in the set when mist fell and umpire Cedric Mourier declined to stop play. After losing his serve, Roddick slammed down his racket, picked it up and threw it again.

Downtrodden U.S. tennis fortunes received a surprising boost when qualifier Taylor Dent upset No. 15 Tommy Robredo 7-5, 6-3.

Dent next plays No. 2-seeded Roger Federer, who beat Nicolas Kiefer for the 11th consecutive time, 6-4, 6-1. Roddick’s next opponent will be No. 9 Gael Monfils, who rallied from two service breaks down in the final set to beat two-time Grand Slam champion Marat Safin 5-7, 7-5, 7-6 (3).

No. 5 Venus Williams, seeking her fourth Key Biscayne title and her first since 2001, beat Anna-Lena Groenefeld 7-5, 6-3.

There were two upsets on the women’s side, both involving last year’s French Open finalists. No. 7-seeded Ana Ivanovic, the defending Roland Garros champion, lost to No. 25 Agnes Szavay 6-4, 4-6, 6-1. No. 2 Dinara Safina was beaten by unseeded Samantha Stosur 6-1, 6-4.