Second-seeded Andy Roddick continued to steamroll his opponents in his quest to repeat his U.S. Open title, making it into the quarterfinals with an ace on match point, erasing No. 18 Tommy Robredo in straight sets, 6-3, 6-2, 6-4, on Tuesday.

Roddick has played the minimum number of sets in the tournament, picking off both seeded players he has faced easily. In each of his previous matches, Roddick lost no more than seven games; he dropped nine to Robredo.

Almost even in unforced errors, Roddick made the difference, as usual, on a serve that topped out at 149 mph, slamming 11 aces. Roddick also cleaned up with 36 winners in the match.

"I played solid, you know," Roddick said. "I'm serving well. I'm breaking a lot. . . . I feel like I'm returning pretty well. I'm moving well. You know, I feel good right now. But the next match is going to be totally different than the four I've played so far, you know. It's going to be a lot of serving."

In the quarterfinals, Roddick is set to play Sweden's Joachim Johansson, the 28th seed, after Johansson beat Michael Llodra, 6-2, 6-3, 6-2, on Tuesday afternoon.

In the day's first match, Lleyton Hewitt continued his strong play of late -- he won his last two tournaments, including the Legg Mason Tennis Classic, coming into the Open -- with a straight-set victory, 6-4, 6-2, 6-2, over Karol Beck to move into the quarterfinals, where he will face the rejuvenated Tommy Haas.

Beck faltered on his own serve and never broke Hewitt, not taking advantage of any of the five chances he had. He also collected 38 unforced errors and seven double faults.

"The first set today the guy played pretty good tennis, I think," Hewitt said of the 72nd-ranked Beck. "Didn't make a lot of mistakes out there. You know, I tried to step it up at 4-all [in the first set], played a good game to break. After that he sort of went away a little bit. I put a lot of pressure on his service games."

Hewitt extended his winning streak to 14 matches. His last loss was to Andre Agassi in the final of a tournament in Cincinnati, just a week before his run to the Legg Mason title.

Hewitt's next opponent, Haas, took out 18-year-old Tomas Berdych in the fourth round, 7-6 (8-6), 6-1, 7-5. Haas struggled a bit through a tight first set, but took control in the second and simply outlasted Berdych in the third.

After missing all of 2003 with shoulder trouble, including two surgeries, Haas has regained some of the form that led to him to the No. 2 ranking in 2002, winning two singles titles this year and now reaching the quarterfinals of the Open.

"Tommy is a class player," Hewitt said. "You know I've got to do small things maybe a little bit different, you know, against Tommy than you do against guys ranked 50 or something in the world. He's a class player who's been in the top five players in the world before."