Southpaw Drew Smyly will undergo Tommy John surgery after tearing the ulnar collateral ligament in his left elbow during injury rehab, the Mariners announced Wednesday.
Smyly will miss the remainder of the 2017 season and at least a majority of the '18 season as well, with the recovery time for Tommy John surgery typically taking between 12-18 months.
Smyly was nearing a Minor League rehab assignment before the UCL tear, most recently throwing a 25-pitch simulated inning on Saturday. At the time, he had been rehabbing for a return from elbow issues he ran into in Spring Training.