HOUSTON -- Astros starting pitcher Roy Oswalt walked off the mound due to a left hip abductor strain after making his warmup tosses prior to the seventh inning Monday in a 4-1 win against the Dodgers.

Oswalt (7-8, 4.60) left the mound with assistant athletic trainer Rex Jones after conferring with Jones and manager Cecil Cooper. Oswalt is listed day-to-day.

"I think I came out before it got real bad," Oswalt said. "I felt it the last pitch in the sixth, and I probably should have told them before I went up to bat, but I thought I may be able to go out there and pitch the seventh, maybe eighth."

Oswalt had allowed one run on six hits with nine strikeouts and no walks, throwing 79 pitches. The right-hander's performance was the best Cooper said he has seen all season, especially in the fifth and sixth frames where he struck out two and three, respectively.

Oswalt, who felt the strain on a curveball to Blake DeWitt, will be reevaluated Tuesday, and he said he's optimistic. The Astros ace told pitcher Oscar Villarreal as he left the clubhouse that he was "hopefully" OK.

"I hope it's just a hip pointer, where your ribs hit your hip," Oswalt said. "We'll see how it feels tomorrow."

Closer Jose Valverde also felt some pain Monday night as he deflected a sharp hit from Angel Berroa in the ninth.

The ball hit off the back of his pitching hand, and he said his ring and pinky fingers were sore after finishing the game.

"We'll check it out tomorrow," Cooper said. "But if I know my big boy, he'll be fine."

Valverde previously took a hit to the jaw May 23 off the bat of Philadelphia's Pedro Feliz. Valverde finished that game.