Clemens, who lasted 5 1/3 scoreless innings, came out of the game after his finger was checked for a third time.
"It's something I've had since high school," Clemens said. "It's happened a thousand times."
Clemens allowed one hit, walked two and struck out three after taking over for starter Erik Bedard with one out in the first inning.
"Erik Bedard and the offense deserved to win that game my last time out," Clemens said. "I was given a 16-run lead in my Major League debut. I owe them the world. To put me in where I could relax and just throw pitches made me want to come out tonight and pick these guys up."
He retired 13 of the 16 batters he faced, saving the Astros' bullpen from possibly being overworked.
He made his Major League debut in his last appearance last Tuesday, earning a win in a game started by Bedard in Seattle.
Rick Eymer is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.