The Astros have won four of five to show some life in what has mostly been a dismal first two months of the season. Houston is 5-2 since losing a season-high seven straight in the middle of May.
The Astros hope Pettitte can get them off on the right foot against the Cardinals.
Pettitte, who has only faced St. Louis once, is 3-5 despite a respectable 3.71 ERA. Pettitte went 2-3 in May, finishing the month with a 2-1 win over the Milwaukee Brewers on Sunday. The southpaw held the Brewers to three hits and struck out eight in six innings.
Pettitte failed to earn a decision after allowing one run and four hits in six innings of Houston’s 4-1 win over St. Louis on April 6.
The Cardinals, who have lost three of five following a five-game win streak, has a comfortable 5 1/2 -game lead in the NL Central. Houston is 13 1/2 games back in sixth place.
Isringhausen suffered his first blown save in 22 tries dating to last season. It was the reliever’s first blemish in a season in which he had converted all 16 of his save opportunities and allowed only one earned run.