The St. Louis Cardinals open a critical stretch of six games against the two teams in front of them in the National League Central tonight as they play Houston. The Astros are 4 1/2 games ahead of the third place Cardinals in the Central. Houston is running three games behind the front-running Cubs after losing to Chicago 6-2 yesterday. The Cardinals will start Matt Morris (12-5) tonight against Houston’s Wade Miller (11-5). This will be a two-game series between these two clubs. The Cards and Cubs will play four beginning on Thursday.