Perhaps the most valuable reliever on this list, if the Cardinals wanted to go big with their bullpen piece, lefty A.J. Puk would be an excellent addition to the club.
Just 27 years old with plenty of team control, Puk stands at 6’7 and his production has been as equally intimidating as his stature. In 28 innings of work for the Oakland Athletics, his 1.93 ERA and 26 SO from the left side would be a welcomed addition to what the Cardinals bullpen currently has.
Perhaps the biggest obstacle for the Cardinals in acquiring his services would be the price tag that Oakland will place on him. They will be in no rush to move him since they still have plenty of control over him, and it is extremally difficult to find left handed relivers this elite. Oakland is in desperate need of prospects, so they will look to get top value for Puk if they were to move him.