The Associated Press

NEW YORK - Andy Roddick unfurled his body and unleashed a 140 mph ace that forced a line judge to duck as the ball slammed against the wall with a thud.

It was the loudest display Roddick produced Sunday in a 6-1, 6-3, 6-3 victory over Flavio Saretta to reach the U.S. Open's fourth round. Roddick was the picture of calm, without a trace of the antics he used to pull - and which his previous opponent derided.

Instead, it was Saretta who clowned around, staring at a line when he thought a call was incorrect, kicking the ball, flipping his racket in the air or cracking it on the ground. The No. 4-seeded Roddick was all business.

"I've been playing like that the past three months," Roddick said. "I just kind of realized I didn't need to fight a mental battle every day."

Andre Agassi doesn't engage in antics these days, too concerned with saving every bit of energy and keeping track of each detail. So Agassi wasn't pleased about not being consulted when his third-round match against Yevgeny Kafelnikov was suspended for nearly 24 hours early in the second set Saturday.

Not that it mattered in the end: The top-ranked Agassi wrapped up a 6-3, 7-6 (4), 6-4 victory Sunday to set up an Old vs. Young meeting with fellow American Taylor Dent in the round of 16. Dent upset No. 15 Fernando Gonzalez Saturday.

"For the match to get called, and to be the only match that didn't finish yesterday, I think was a mistake, an oversight in judgment," the 33-year-old Agassi said.

Among his complaints: The Dent-Gonzalez match also should have been delayed a day so that winner wouldn't get more rest.

"It gets harder as you get older for a number of reasons," Agassi said. "Between your body and your mind, your heart, the energy, the focus, the determination, the eagerness, the freshness - all those things get tougher."

Agassi was down a break in the second set when the match resumed. He began Sunday by breaking right back, then held for a 2-1 lead with a backhand winner down the line that drew a thumb's up of approval from two-time major champion Kafelnikov.

Agassi trailed again by a break later in the second set, but got it back in the 10th game, winning four straight points with the help of a crosscourt forehand return that caught a line. He again took four consecutive points in the tiebreaker, winning it when Kafelnikov sent a backhand long.

"He played just as good as he did four years ago, maybe even better," said Kafelnikov, referring to the last time Agassi won the Open. "Normally, if you are getting older, you are becoming physically weaker. With him, it's the opposite."

Agassi, the oldest top-seeded man in the Open era, makes sure everything is exactly to his specification on court. He wants the umbrella held just so to block the sun, wants his towel in a certain spot, wants precisely the right ball to serve.

Roddick didn't have to trouble himself too much with such minutiae.

The only man to reach two major semifinals in 2003 lost just three of 35 points during his service games over the first two sets Sunday. He avoided a break point until the match's very last game. Younes El Aynaoui beat Jiri Novak 7-6 (1), 5-7, 3-6, 6-3, 7-6 (5) to set up a fourth-round match against No. 7 Carlos Moya, who beat Nicolas Massu 7-5, 6-4, 3-6, 6-3.

No. 12 Sjeng Schalken, a 2002 semifinalist, ended the run of qualifier Ivo Karlovic 7-6 (8), 7-6 (5), 7-6 (3), and will meet No. 8 Rainer Schuettler, runner-up to Agassi at the Australian Open in January. Schuettler beat Alberto Martin 6-1, 6-4, 6-2.

The only past champion in the women's field, third-seed Lindsay Davenport, advanced to the quarterfinals by defeating No. 19 Nadia Petrova 6-0, 6-7 (6), 6-2. Davenport will play No. 24 Paola Suarez, who got past Elena Likhovtseva 6-2, 3-6, 7-5.

At a glance

Men: No. 1 Andre Agassi, No. 4 Andy Roddick, No. 8 Rainer Schuettler and No. 12 Sjeng Schalken won in straight sets. No. 7 Carlos Moya beat Nicolas Massu in four sets. No. 22 Younes El Aynaoui needed a fifth-set tiebreak to upset No. 10 Jiri Novak.

Women: No. 3 Lindsay Davenport beat No. 19 Nadia Petrova. No. 5 Amelie Mauresmo and No. 24 Paola Suarez also won their matches.

TV: 12, 7: 11 a.m.-6 p.m. (live), 12:37-1:07 a.m. (highlights); USA: 7-11 p.m. (live); 2-4 a.m. (tape).