St. Louis already has a proven closer in Trevor Rosenthal, an All-Star last season who finished with a 2.10 ERA and second in the National League with 48 saves. GM John Mozeliak confirmed that Rosenthal will still close and Oh will serve as a setup man with the Cardinals.
Because Oh's contract with the Hanshin Tigers is up, he was a free agent and not subject to the posting system. His move to the Majors comes after the KBO issued a suspension for half a season to Oh for his connections to gambling with a former teammate at a casino abroad, which is forbidden by South Korea laws for its citizens.