"When you have an opportunity to bring the expertise and experience of a future Hall of Famer to your club, it's easy to see why we are excited about the prospects of what John Smoltz can do to improve our team's chances as we approach the stretch drive," Cardinals General Manager John Mozeliak said.
Smoltz, an eight-time all-star, was released by Boston Monday after going 2-5 with an 8.33 ERA in eight starts (40 innings).
Off-season shoulder surgery and subsequent rehab delayed his Red Sox debut until June 25.
The 1996 National League Cy Young Award winner was designated for assignment Aug. 7, less than 24 hours after giving up nine hits and eight runs with four walks in a start against the New York Yankees.
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