Juan Martin Del Potro saw his nine-match U.S. Open winning streak come to an end as the 2009 champion fell 4-6 7-6 6-2 7-6 to France's Gilles Simon in the third round on Sunday at Flushing Meadows.
Del Potro, who beat Rafa Nadal and Roger Federer on his way to his first grand slam title at the National Tennis center, missed last year's championship following wrist surgery.
The 18th-seeded Argentine has made an encouraging comeback from the injury this year with titles at Delray Beach and Estoril, but was not quite at full force.
"He's a fighter, no?" Del Potro said in admiration of 12th seed Simon. "It's very hard to make a winner playing against Simon. But I tried until the end."
The big-serving Del Potro, showing signs of fatigue on a hot, muggy day, lost the second-set tiebreaker 7-5 and the final decider 7-3.
"I play at lower level in the tie-breaks," he conceded. "He took the chance and he closed the match in the fourth set.
"Anyways, I''m glad to be here, playing this tournament. I feel a little sad now because I just lost. But I think my comeback is in good shape. I'll keep trying to improve my game."
There was plenty of reason to cry for Argentina, as David Nalbandian fell to Rafa Nadal and Juan Ignacio Chela lost to American wildcard Donald Young.
Del Potro said it has been difficult for him to rebound from nine months on the sidelines.
"It's not easy after a year out of competition to come to the grand slam and play five sets with this weather," he said.
"I'm still trying to recover my game, my fitness, my mind, everything. I know that takes a long time, but I''m doing faster than everybody thinks.
"Hopefully I'll be ready or be better for the next grand slam next year."
