CHICAGO (AP) _ Houston Astros right-hander Roy Oswalt left Friday's game against the Chicago Cubs early after aggravating a strained groin.

``Any time you have to deal with pain like that, you can't throw the ball where you want it,'' said Oswalt, who lasted just three innings and lost his first start since July 23. ``It's a sharp pain. Once you get to the critical point where you release the ball, that's when it kicks in.''

Oswalt had missed his previous start after straining his groin Sept. 18 in San Francisco. He lasted only two innings against the Giants, his first start in nine days.

Though the temperature at the start of the game was only 56 degrees, Oswalt said he felt good at first. It wasn't until he faced Sammy Sosa in the third inning that he felt pain.

``The first couple innings, I didn't feel anything, so I thought I'd crank it up a bit,'' he said. ``The second at-bat against Sammy, the second pitch against him, it felt like something pulled. Every pitch since, it hurt some.''

Oswalt stayed in the game, giving up two more runs and three hits before getting out of the inning. He allowed a total of four runs and nine hits in three innings.

``I just tried to do too much,'' he said.