NEW YORK  For so many years the male standard-bearer for U.S. tennis, Andy Roddick is enjoying seeing the success of some other Americans.

Now, though, he'll have to face one of them.

The 2003 U.S. Open champion pounded 13 aces, didn't face a break point until the final game and easily eliminated 81st-ranked Marc Gicquel of France 6-1, 6-4, 6-4 Thursday night to reach the third round at Flushing Meadows.

Roddick improved to 4-0 against Gicquel, winning all 11 sets they've played.

The fifth-seeded Roddick next will take on 55th-ranked John Isner in an all-American matchup with a berth in the fourth round at stake. The 6-foot-9 Isner beat Marsel Ilhan of Turkey 6-3, 6-4, 7-6 (1).

"I mean, it's a completely different matchup. There's a lot more against John that's out of my hands. I know he's going to come out and just play super, super aggressive," Roddick said. "I'm just going to have to stay the course. There will probably be some ups and downs. Kind of just try to get through it."

Three other U.S. men also advanced Thursday: No. 21 James Blake, No. 22 Sam Querrey and 276th-ranked qualifier Jesse Witten.

"This is a tournament that most guys want to do well in. We're gearing up for this tournament all summer long, really putting 100 percent of our focus into this one," said Isner, who took a set off Roger Federer before losing to him in the third round of the 2007 U.S. Open. "This is the surface most of us excel at."

On the women's side, Melanie Oudin, a 17-year-old from Marietta, Ga., pulled off the biggest upset of the tournament when she stunned No. 4-seeded Elena Dementieva in three sets Thursday.

Roddick caught some of that match and Witten's.

"I like the way she constructs points. It's not just, you know, hitting the ball to one spot. She kind of works the slice in there. She competes. She moves really well," he said. "She seems like a sweetheart. I'm cheering for her. I like watching her play."

Roddick and Witten competed against each other as kids growing up in Florida. While Roddick has played in five Grand Slam finals and reached No. 1 in the rankings, Witten never had won a tour-level match as a professional until this week.

So how good was Witten, way back when?

"Not the best. He's certainly improved," Roddick said.

He related a conversation the pair had before U.S. Open qualifying, when Witten spoke about not being sure how much longer he'd stay on the profession circuit.

"All of a sudden," Roddick said, "he's here in the third round."