Federer beat Baghdatis 7-6 (5), 7-5, shortly after David Ferrer ousted defending champion Andy Roddick 7-6 (4), 6-4. Only four seeds remained, including James Blake, who had an evening match.

"It was a struggle out there for both of us," Federer said. "It was tough to keep the ball in play, you know, it was really quick."

Baghdatis has never beaten Federer in five matches, but pushed the No. 1 player in the world as he did a year ago in the Australian Open, when Federer won in four sets.

"Basically, I gave the first set away," said Baghdatis, who helped Federer fight off two set points with a double-fault. Federer then won the tiebreaker, winning the first and last points with aces.

"I couldn't imagine losing the first set, but I did," Baghdatis said. "Basically, he won the first set because of his name — Federer. I can say that because I choked."

Third-seeded Roddick was the 11th seed to fall. No. 2 Rafael Nadal had retired yesterday with cramps in his wrist and arm, and No. 4 Novak Djokovic lost to Carlos Moya, who stayed alive today by beating Juan Martin Del Potro of Argentina, 7-5, 3-6, 7-5 in a match in 110-degree heat on center court.

Only four seeds remained when No. 5 Nikolay Davydenko beat No. 10 Tomas Berdych 6-3, 6-2. Earlier, Lleyton Hewitt topped Jurgen Melzer 6-3, 6-3; Nicolas Almagro defeated Jarkko Nieminen 6-2, 6-2; and Sam Querry downed Juan Monaco 6-3, 7-5.

Federer, who is seeking his 50th title, said despite his erratic performance today he felt he was in the flow of the tournament. He will face Almagro in tomorrow's quarterfinals.

"I have to stay aggressive and probably have to play a bit better than I did today," Federer said. "Hope I can concentrate on my serve and hold on to that and create chances."

Hewitt said fighting the heat was a physical and mental challenge.

"It makes you go for wrong shot selections more times, I think, because you're trying to finish the point off, you know, because it's so hard to keep playing long rallies in these kind of situations," he said. "You really have to pick and choose the right ones to go for then."

Roddick won the event in 2003 and 2006. He reached the quarterfinals in 2002, semifinals in 2004 and finals in 2005, when he lost to Federer.

After both he and Ferrer held serve en route to a tiebreaker, Roddick lost the first three points, starting with a double-fault. He finally won two points when Ferrer couldn't handle serves of 141 and 142 mph, Roddick's best of the set, and won another point with a 140 mph ace.

Ferrer closed out the tiebreaker with solid ground strokes, and Roddick threw his racket in disgust when his return on set point went wide.

Both players held throughout the second set until Ferrer broke Roddick in the 10th game.

"I just didn't do anything that I've been working on," Roddick said. "I was standing too far back. I wasn't imposing myself, and I was giving away free points. All the way around, it was a pretty ordinary performance."

But Roddick said there is plenty of time to get himself righted before the U.S. Open.