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 in 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.

The match forced the cancellation of plans for Roddick and tennis buddy Mardy Fish to play H-O-R-S-E against Wade on the Miami Heat practice court following their workout Sunday.

"He can have his H-O-R-S-E title for another year," Roddick said. "It's disappointing, and it's something I really looked forward to."

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.

"I basically was wondering how many more times we were going to play on a slippery court," Roddick said. "He said, 'Well, no one has fallen yet.' I said, 'Well, if that's a barometer, then we have a problem.' So I feel like my argument was just, but the way I went about it probably wasn't the best."

Roddick said he apologized to Mourier after the match.

Downtrodden U.S. tennis fortunes received a surprising boost when qualifier Taylor Dent upset No. 15 Tommy Robredo 7-5, 6-3. Dent, ranked 467th, is mounting a comeback from a back injury that plagued him for three years.

Only four American men — including Roddick and Dent — and two women — the Williams sisters — remained in the tournament when the third round started Sunday.

Dent next plays No. 2-seeded Roger Federer, who beat Nicolas Kiefer for the 11th consecutive time, 6-4, 6-1.

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.

That left the women without three of their seven highest-seeded players. No. 3 Jelena Jankovic was eliminated Saturday night by Gisela Dulko.

Roddick missed many chances in the first set to make his match shorter. With the No. 25-seeded Tursunov serving at 5-all, Roddick failed to convert five break-point chances and finally sailed a forehand long to lose the 22-point game. He also was unable to convert his first three set points in the tiebreaker.

Roddick said gusty wind and high humidity made conditions difficult, so he was content to keep the ball in play and wear Tursunov down with a series of long rallies.

"It's like a swamp out there today," Roddick said. "You're sweating a ton. I mean, you can wring out your shorts afterward. So I wanted to be sure to take advantage of that and make the points tough."

The match started at 11 a.m., and Roddick said he didn't know until afterward that his agent and trainer had scrubbed the H-O-R-S-E showdown because they feared he might be late.

"They said they had to make a call this morning," Roddick said. "Obviously Dwyane wasn't waiting around all day, and so my agent erred on the side of not making Mr. Wade wait."

Roddick, who often disparages his basketball skills, said Wade is his favorite athlete. Rescheduling their game wasn't an option because the Heat play at home Monday, then have a three-game trip starting at Dallas.

Said Roddick: "I don't know if I provide the necessary warmup for the Mavericks."