The Brewers selected Thomas with the 13th pick in the Rule 5 draft Wednesday, JJ Cooper of Baseball America reports.
Thomas, a 26-year-old lefty the Brewers are poaching from the Cardinals, had operated primarily as a starter until last season, in which 53 of his 56 appearances at Triple-A were out of the bullpen. He logged a 2.89 ERA, 1.34 WHIP, 79:24 K:BB in 90.1 innings, so while he worked as a reliever, he is stretched out enough to move back to the rotation this year if the Brewers wanted to go that route at some point. More likely, Thomas will work as a low-leverage multi-inning reliever for Milwaukee or be returned to St. Louis at some point this season.