LOS ANGELES, July 28: Top seed Andy Roddick overcame spirited resistance from fellow American Scott Oudesma before advancing to the Los Angeles Open quarter-finals with a 6-7 6-3 6-2 victory on Thursday.

However, Roddick suffered an abdominal muscle strain late in the match and is considering withdrawing from the event with the U.S. Open looming large next month.

“I hit the one passing shot and strained something in my side,” a subdued Roddick told reporters. “It doesn't feel too good right now.

“If it's like this tomorrow, I don't think there's a lot of hope.

“Once it happened, it was always there. When I served, and pretty much on every shot, there was pretty intense pain.

“I didn't play my best stuff but I got through tonight,” added the world number 10, who unleashed 21 aces before setting up a last-eight meeting with Russian Dmitry Tursunov.

Wild card Oudesma, playing only his second ATP event, matched Roddick with power serves and crunching ground strokes in the opening set but lost momentum as his more experienced opponent upped his game.

Fourth seed Robby Ginepri, below top form for much of this season, also had to fight hard before claiming his place in the last eight, outlasting Denmark's Kenneth Carlsen 7-6 3-6 6-4.

The American took the first set on a tie-break but was outplayed by Carlsen in the second after being broken in the fourth game.

Ginepri appeared to hold the upper hand in the deciding set after breaking the Dane's serve for a second time to lead 4-1.

But both players then struggled to hold serve in a wildly fluctuating finish, the American being broken in the seventh and ninth games and the Dane in the eighth and 10th.

Results (second round): Dominik Hrbaty (SVK x7) bt Lars Burgsmuller (GER) 7-5, 6-4; Dmitry Tursunov (RUS x8) bt Sam Querrey (USA) 7-5, 6-4; Robby Ginepri (USA x4) bt Kenneth Carlsen (DEN) 7-6 (7/5), 3-6, 6-4; Andy Roddick (USA x1) bt Scott Oudsema (USA) 6-7(3) 6-3 6-2.

ZVONAREVA WINS