Fish withdraws from US Open before Federer match

The 30-year-old American, who was seeded 23rd at Flushing Meadows, missed about 2½ months this season because of an accelerated heartbeat and had a medical procedure in May.

"We are not 100 percent sure what the issue is and if it is related to his previous issues," Fish's agent, John Tobias, wrote in an email to The Associated Press. "Mardy is fine and will return home to L.A. tomorrow. This was strictly precautionary and I anticipate that Mardy will play in Asia this fall."

Fish's departure means 2003 champion Andy Roddick is the only American man left in the field. Roddick, who announced last week that he'll retire after the U.S. Open, plays 2009 champion Juan Martin del Potro in the fourth round Tuesday night.

Fish's third-round victory over Gilles Simon at the U.S. Open went five sets, lasting more than 3 hours and ending after 1 a.m. Sunday. Afterward, Fish did not attend a news conference; the tournament said he was getting medical treatment, but didn't elaborate.

In a statement released by the U.S. Tennis Association on Monday, Fish said he "was reluctant to" withdraw from the year's last Grand Slam tournament but was "following medical advisement." He added that he looks forward "to resuming my tournament schedule in the fall."