MASON, Ohio (AP) _ In a week in which so many seeded players at the Cincinnati Masters have fallen, No. 7 seed Andy Roddick seems to be getting stronger _ as the U.S. Open draws closer.
He fended off a vigorous challenge Thursday night by unseeded James Blake, 7-6 (2), 6-2 to advance to the tournament's quarterfinal round, then disagreed when told his rivals say he is the player to beat in the Open, which begins on Aug. 25. But, Roddick did say that his confidence is building.
``I can definitely imagine myself winning a Grand Slam now,'' he said. ``A couple of months ago, I couldn't.''
He faces Argentina's Mariano Zabaleta on Friday afternoon. Zabaleta advanced on Thursday night by outdueling Flavio Saretta, 6-7 (5), 6-2, 6-4.
Roddick, Guillermo Coria and Rainer Schuettler went into the quarterfinals as the only seeds still playing out of the original 16. Defending champion Carlos Moya was eliminated in the first round Monday to start the week of upsets.
Roddick and Blake traded power serves and precise returns before the seventh-seeded Roddick wore down his opponent in the second set. Roddick has now won all seven times they have played.
Blake said that in the year since they last played, Roddick has learned to change speeds on his serves, alternating between 140 mph and 120 mph.
``He changes up on it a little,'' Blake said. ``Any time he gets in trouble, he steps up his serve. It's a great weapon to have.''
The emotion of the match was evident, with Blake crying out and Roddick throwing up his hands when their shots went astray. At one point when Blake trailed four games to two in the second set and one of his returns was ruled out of bounds, he walked over to chair umpire Norm Chryst and asked about the call before returning to the court.
Blake told reporters later that he still thought his shot was in bounds and suggested that tennis should use ``Spot Shot'' replay technology to trump possible human error.
``Humans are fallible,'' Blake said. ``Spot Shot's supposed to be accurate. Why not use it?''
Roddick dismissed Blake's complaint, saying the disputed shot was out.
The crowd gave both players a standing ovation as the match ended and Roddick and Blake met at the net to shake hands.
The sixth-seeded Coria needed just an hour and 15 minutes to beat Mikhail Youzhny 6-2, 6-1.
Schuettler, the No. 8 seed, outlasted Todd Martin 7-5, 3-6, 6-3. Martin hung on to push Schuettler despite suffering eight double-faults to Schuettler's three. Martin also had 32 unforced errors to his rival's eight.
Coria said he wasn't surprised by the elimination of so many seeded players.
``Today, tennis is really, really very competitive,'' the Argentine said through an interpreter. ``It's been happening the whole year, these upsets.''
The suburban Cincinnati tournament has not had an unseeded finalist since Chris Lewis in 1981, and he became a straight-set loser to John McEnroe, the No. 1 seed then.
In other matches Thursday, Mardy Fish defeated Arnaud Clement 6-2, 6-2; Robby Ginepri beat Gaston Gaudio 6-1, 7-6 (4); David Nalbandian topped Juan Ignacio Chela 6-4, 6-4, and Max Mirnyi eliminated Hicham Arazi 6-4, 6-7 (7), 6-4.
On Wednesday, 2002 Wimbledon runner-up David Nalbandian beat reigning Wimbledon champion Roger Federer 7-6 (4), 7-6 (5). Nalbandian has defeated Federer _ the No. 3 seed in this tournament _ all four times they have played.
Other seeded players who have been eliminated include Lleyton Hewitt, Sebastien Grosjean, Gustavo Kuerten, Paradorn Srichaphan, Jiri Novak and Tommy Robredo. Top-seeded Andre Agassi dropped out of the tournament last week, saying he needed a break before playing in the U.S. Open.