The Cardinals selected Shuster's contract from Triple-A Memphis on Tuesday.
Since his last appearance in the big leagues May 6, Shuster has turned in a 9.00 ERA and 2.39 WHIP alongside a 16:14 K:BB across 18 innings with Memphis. Despite his poor performance, he'll return to the Cardinals' bullpen to give the big club a fresh arm for the second game of its doubleheader against Milwaukee. Bruce Zimmermann was designated for assignment in a corresponding move.