New York ? The worst birthday of Andy Roddick’s life ended with three straight tiebreak losses and a shocking first-round exit from the U.S. Open against a player making his debut in the tournament.

Roddick, the champion two years ago and the No. 4 seed this year, fell, 7-6 (4), 7-6 (8), 7-6 (1), on his 23rd birthday Tuesday night to Gilles Muller, the first man from Luxembourg to compete in the Open.

The 22-year-old Muller, ranked No. 68, outhustled, outmaneuvered and, most astonishingly, out-aced Roddick, 24-17, to claim his second huge upset of the summer. In his first Wimbledon, he beat French Open champion Rafael Nadal.

Asked how he managed to dismantle Roddick, Muller replied sheepishly, “I have no idea.”

“For me, it was just unbelievable to come out here today,” Muller said. “I told myself to enjoy it, and I did every minute.”

Roddick hated every minute of it after blowing a 5-2 lead in the first set and a chance to serve out that set at 5-3.

From then on, Roddick was frustrated by the left-handed Muller’s canny mix of angled groundstrokes and serves, his blend of speeds and his amazing ability to hit line after line.

Roddick flung his racket to the ground, dropped it another time in disgust and kept chomping on a towel during changeovers. More than a few times he stared at the lines where Muller’s shots landed, as if not believing his eyes, or watched the replays on the giant screen atop the stadium.

“I don’t really remember a loss where I’ve felt this bad afterwards,” Roddick said. “I love playing here. I probably had the best practice week I’ve ever had in leadup. It just didn’t translate tonight. … I’m in a little bit of shock right now, to be honest. I’d give anything to go back four hours right now.”

James Blake defeated former finalist Greg Rusedski in the afternoon. Backed by his friends and many fans chanting “James! James!” in Arthur Ashe Stadium, Blake served a 131-mph ace to reach match point, then ripped a backhand passing shot to beat the No. 28 Rusedski, 7-5, 7-6 (3), 6-3.

Unseeded, James may not be a threat to win the Open. He’s playing the best tennis of his life at age 25, but he harbors no illusions that he’s in the same class as No. 1 Roger Federer, who won his first-round match against Czech newcomer Ivo Minar, 6-1, 6-1, 6-1, in 1 hour, 1 minute earlier in the day, or the No. 2 Nadal, who could end Blake’s run in the third round.