Blewett has exercised an opt-out clause in his minor-league contract with the Cardinals, Derrick Goold of the St. Louis Post-Dispatch reports.
The Cardinals now have the choice of either adding him to their 40-man roster or letting him depart as a free agent. Blewett has spent the entire season at Triple-A Memphis, holding a 5.18 ERA and 63:19 K:BB over 48.2 innings.