The Cardinals claimed Alcala off waivers from the Red Sox on Thursday.
Alcala has split time between the Twins and Red Sox this season, posting a 6.64 ERA and 46:23 K:BB over 40.2 frames. The 30-year-old reliever cannot be optioned to the minors, so he will go onto to the Cardinals' active roster. St. Louis will have to make a corresponding transaction once Alcala officially reports to the club.