Kyle Gibson, the Twins' top pitching prospect, has an elbow injury that could require Tommy John ligament replacement surgery.
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Though Rantz mentioned the ulnar nerve, the team also is concerned it might be the ulnar collateral ligament, the one commonly replaced now for pitchers through the Tommy John procedure. Francisco Liriano, Joe Nathan, Carl Pavano and Brian Duensing are among the Twins pitchers who've had Tommy John surgery.