Double-A Springfield activated Hjerpe (elbow) from the 60-day injured list Thursday.
Hjerpe had Tommy John surgery last April and has completed a rehab assignment, allowing four runs with a 9:3 K:BB over 8.2 innings covering five starts between Single-A Palm Beach and the rookie-level Florida Complex League. The left-hander struck out four over three scoreless frames in the FCL his last time out and will continue to get stretched out in the Springfield rotation. Hjerpe is on the Cardinals' 40-man roster and should move up to Triple-A Memphis before long if he's pitching well. A major-league debut during the second half is possible.