Liberatore (back) was activated from the 15-day injured list Monday.
Liberatore didn't pitch well in two rehab starts with Triple-A Memphis, allowing six runs while walking 10 over 6.2 innings. He brought his pitch count up to 83 in his last outing Sunday, and the Cardinals have decided he's ready to join the big club, despite his poor results in the minors. St. Louis presumably wants to stick Liberatore back in its rotation, though it's unclear when he might make his next start.