Mayers (lat) was activated from the 60-day injured list Tuesday.
Mayers has been on the shelf since mid-April due to a right lat strain, but after completing his rehab stint at Triple-A Memphis, he's ready to return to the big-league bullpen. He's appeared in eight games this season for St. Louis, posting a 5.40 ERA with eight punchouts over 8.1 innings of work. Chasen Shreve was designated for assignment in a corresponding move.