DENVER -- Anticipating a tough night for left-handers, manager Cecil Cooper posted an all-righty starting lineup for Saturday's game against Rockies southpaw Jeff Francis.

Cooper assigned left fielder Ty Wigginton to the leadoff spot, which he often does when the Astros face a particularly tough left-hander. Wigginton left the game after straining his left groin in his first at-bat, and Cooper inserted left-handed-hitting Darin Erstad to replace him in the outfield.

Cooper played Jose Castillo at third, and Reggie Abercrombie in center instead of Michael Bourn..

Cooper based his decision on the numbers. Left-handers were hitting .257 against Francis, where as righties were hitting .295.

"I'm trying all the right-handers I can with this guy," Cooper said. "There's a 40 point difference. Left-handers haven't fared well against him."

Cooper might go with the same lineup Sunday against lefty Jorge De La Rosa, but he may want to think twice before doing so. Lefties are hitting .304 against him, while righties are hitting .256.