Fourth-seeded John Isner was bundled out of the Delray Beach Tennis Championships in the first round on Monday after a 6-4, 5-7, 7-6 (13) loss to 76th-ranked Teymuraz Gabashvili of Russia.
Isner failed to take advantage of four match points in the final set tiebreaker.
The American helped Gabashvili win the match on his fifth match point in the tiebreaker when he double-faulted away the final point.
Isner was clearly upset by the loss and was not in the mood to answer questions.
"I didn't play well," he said.
Gabashvili will play the winner of the match between 2009 U.S. Open champion Juan Martin del Potro of Argentina and Richard Berankis of Lithuania.
"In the end he just went for his first serve," Gabashvili said. "He had four match points he saved, but he just went for it there and in the end it went for me."
Earlier, top-seeded Andy Roddick withdrew from the tournament due to flu-like symptoms. The eighth-ranked American complained of feeling ill before winning the RMK Championships title over Milos Raonic 7-6, 6-7, 7-5 on Sunday.
"I'm very disappointed," he said. "I've waited too long to come back and play this tournament. But with traveling internationally (for Davis Cup) and Palm Springs and Miami coming up on that, it's just unfortunate timing for this sickness."
The top four seeds in the Delray Beach tournament were all Americans, with Roddick followed by 2009 champion Mardy Fish, Sam Querrey and Isner. Qualifier Marinko Matosevic of Australia took Roddick's spot in the draw and will face Dudi Sela of Israel in the first round.
The third-seeded Querrey moved into the second round with a 6-3, 5-7, 6-3 win over Dustin Brosn of Germany, while James Blake of the United States beat No. 7-seeded German Benjamin Becker 7-5, 6-4.
Florent Serra of France defeated American wildcard Ryan Harrison 3-6, 6-3, 7-5 in another first round match and Brazilian Ricardo Mello rallied to down Rainer Schuettler of Germany 2-6, 6-2, 6-3.