World No. 1 Roger Federer advanced into his 34th consecutive Grand Slam quarter-final without touching a racquet on Monday when American Mardy Fish withdrew from their US Open match for health concerns.
The 31-year-old Swiss star, seeking his 18th Grand Slam title and sixth US Open crown, reached a last-eight matchup with Czech sixth seed Tomas Berdych, who dispatched Spanish 11th seed Nicolas Almagro 7-6 (7/4), 6-4, 6-1.
"It will be a tough match against Tomas," Federer said. "We have played many times in the past and he has always been a tough opponent. I will have to continue to serve well and dictate the points."
Berdych has lost 11 of 15 career meetings to top seed Federer.
"I probably need to have something more than 100 percent," Berdych said.
British third seed Andy Murray, the reigning Olympic champion, will face Canadian 15th seed Milos Raonic later for a last-eight berth against Croatian 12th seed Marin Cilic, who beat Slovakian Martin Klizan 7-5, 6-4, 6-0.
The walkover stretched Federer's record for career quarter-final Grand Slam appearances in the Open era to 38, three shy of the record 41 achieved by American Jimmy Connors.
"I am really sorry for Mardy," Federer said. "I just want to wish him a speedy recovery. We all want to see him back on tour soon."
Fish, 30, missed two months earlier this year with a heart problem after his heart rate increased to three times its normal resting pace. He underwent a cardiac catheter ablation in Los Angeles on May 23 to treat his condition.
But he did not say in a statement that a heart issue is what forced him out.
"I regret that I have to withdraw from the US Open for precautionary measures," Fish said. "I was reluctant to do so, but am following medical advisement.
"I had a good summer and look forward to resuming my tournament schedule in the fall."
Federer, who won his 17th Grand Slam title in July at Wimbledon, has not dropped a set in the Flushing Meadows fortnight.
"Maybe if I would be in his situation I would rather play a match and win it and keep the rhythm of one day a match, one day off," Berdych said. "But probably he's going to be fine with that."
Berdych, who took only two hours to reach his first US Open quarter-final, has won three of his past six meetings with Federer, including a US Open tuneup last year at Cincinnati and a 2010 Wimbledon quarter-final.
Berdych finally reached the last eight after 10 tries with his 200th career hardcourt triumph. He joined Petr Korda and Ivan Lendl as the only Czech men in the Open era to have reached the quarter-finals at all four Grand Slam events.
"I'm very happy that I can compete in all Grand Slams at least in quarter-finals. It helps my confidence," Berdych said.
At last January's Australian Open, Berdych was fuming at Almagro, accusing the Spaniard of hitting a ball at him on purpose. The struck him in the arm while at the net during a rally in a fourth-round match.
Spectators booed Berdych for refusing to shake hands with the Spaniard after the match, but the Czech said Almagro's apology was not enough to satisfy him.
Berdych dismissed the acrimonious incident this week as "nothing at all" and they clasped hands after the match, Almagro flashing a quick smile as they met.
Almagro, 27, hopes to replace injured Rafael Nadal on the Spanish Davis Cup team that will host the United States next week in a semi-final tie.
"Knowing Rafa like I know him, he will be climbing the walls," Almagro said. "The most important thing is that he will have time to recuperate so he will come back the same player that he was."
Almagro is unbeaten in four Cup singles matches so far this year.
Berdych, whose best Grand Slam result was a 2010 Wimbledon final loss to Nadal, improved to 7-3 lifetime against Almagro and snapped a five-game losing streak to top-20 rivals dating to a Rome victory over Almagro last May.
Berdych took three of the last four points to win the first-set tie-breaker, a forehand volley winner claiming the set after 48 minutes. He broke Almagro in the seventh game of the second set and at love to start the third as well in the final game.
"It was really close, especially in the first set," Berdych said. "It was a fight for every point. It was a tough match."
Cilic took his eighth victory in a row over a left-handed foe.
"I played really well in crucial moments," he said. "I like to play them. That game suits me. I play well from both sides so it's hard for them to find an opening."