Per MLB Trade Rumors Jesse Hahn underwent surgery on the UCL surgery
Royals righty Jesse Hahn underwent surgery on the ulnar collateral ligament in his pitching elbow, as Rustin Dodd of The Athletic was among those to report on Twitter. Hahn is expected to require approximately six months of rehabilitation, indicating that he may or may not be ready to return for the start of camp next spring.
Fortunately, Hahn did not require the famed Tommy John surgery that is often necessary to fix UCL damage. Instead, he will become the latest pitcher to undergo a “primary repair” procedure. The alternative approach comes with the promise of a much shorter rehab timeline, though it is also not nearly as established as the standby TJS.