Pettitte was a late scratch from the series opener on Monday for precautionary reasons after twisting his left ankle while shagging fly balls during batting practice on Saturday in Milwaukee. Because the Astros called up Taylor Buchholz to make a spot start on Tuesday, the club simply flip-flopped the two pitchers.
The Astros will also look to end a scoreless streak that reached 20 innings after their 7-0 loss on Monday. They haven't scored since Lance Berkman launched a towering 500-foot homer off the scoreboard at Miller Park on Saturday night.
The Astros have some ground to make up. They're 4 1/2 behind the Padres in the Wild Card race, and they trail the Cardinals by six games in the division.
HOU: LHP Andy Pettitte (13-13, 4.34 ERA)
Pettitte was cruising against the Phillies in his last start before he "ran out of gas," according to manager Phil Garner. Still, Pettitte and the bullpen found a way for that not to cost him. He allowed two runs (one of which was caused by his own fielding error) on seven hits in 6 2/3 innings. Pettitte said that he felt fine physically after throwing his 104 pitches -- just 30 of which went for balls. The lefty has faced the Redbirds three times this year, picking up two wins and a no-decision, while giving up three runs each time.
STL: RHP Jeff Weaver (6-14, 5.85 ERA)
Lately, Weaver has been more like the pitcher the Cards hoped they were getting when they acquired him from the Angels. Although he got himself into some jams on Thursday, he pitched five decent innings to get the win against the Diamondbacks. He has been very effective over his last seven starts, registering a 3.64 ERA in that time.
Player to watch
Brad Ausmus is hitting .429 (6-for-14) with two doubles against Weaver.
Wednesday: Astros (RHP Roy Oswalt, 12-8, 3.15) at Cardinals (RHP Jason Marquis (14-14, 5.66), 1:10 p.m. CT
Friday: Phillies (TBA) at Astros (RHP Roger Clemens, 6-4, 2.27) 7:05 p.m. CT
Alyson Footer is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.