Thomas had his contract purchased from Triple-A Memphis on Tuesday.
The Cardinals added Thomas to their 40-man roster in order to protect the 23-year-old from the upcoming Rule 5 draft. He spent most of the 2018 season with Double-A Springfield, slashing .260/.337/.487 with 21 homers and 13 steals across 100 games before earning a promotion to Memphis. He hit .275/.321/.496 with six homers and four stolen bases in 32 games the rest of the season with the Redbirds. Thomas could make his way to the majors in 2019, though it would likely take multiple injuries for him to land in a significant role.