NEW YORK (AP) - Mardy Fish has pulled out of his fourth-round match against Roger Federer at the U.S. Open for precautionary health reasons.
The 30-year-old American missed about two months this season because of an accelerated heartbeat and had a medical procedure in May.
His agent, John Tobias, says "we are not 100 percent sure what the issue is and if it is related to his previous issues." Fish said in a statement Monday he was "reluctant" to withdraw but is following medical advice.
His third-round match against Gilles Simon went five sets, lasting more than 3 hours and ending past 1 a.m. Sunday. Afterward, the 23rd-seeded Fish did not attend a news conference. Tournament officials said he was getting treatment, but didn't elaborate.
The top-ranked Federer reaches his 34th consecutive Grand Slam quarterfinal.