Roger Federer progressed to the quarter-finals of the US Open without hitting a ball on Monday as Mardy Fish pulled out of their scheduled fourth-round match for health reasons.
The American needed minor surgery earlier this year to correct an irregular heartbeat and admitted after his five-set second-round win over Nikolay Davydenko that doubts over his health remained.
Fish then had another long match against Gilles Simon in the third round, after which he did not do a press conference because of medical reasons.
The 30-year-old did not practise yesterday and, although no further explanation has been given for his withdrawal, it is believed to be because of worries over his heart.
The walkover means Federer extended his record of consecutive grand slam quarter-finals to 34, and in the last eight on Wednesday he will play sixth seed Tomas Berdych.
The Czech has looked in fine form this tournament and reached his first quarter-final at Flushing Meadows with a dominant 7-6 (7/4) 6-4 6-1 victory over 11th seed Nicolas Almagro.
The first set was tight but Berdych gradually wore down Almagro and in the third set the Spaniard cut a frustrated figure.
Berdych and Federer have met 15 times before, with the Swiss player winning 11 of them, but Berdych did win their quarter-final clash at Wimbledon in 2011 before going on to reach his only grand slam final.