Following a consultation with specialist Lewis Yocum, Cleveland announced that Tomlin will undergo Tommy John ligament-replacement surgery on his right elbow.
The procedure will be performed by Yocum on Wednesday in Los Angeles and the timetable for recovery is estimated at 12-18 months.
Tomlin had received the same diagnosis from team doctor Mark Schickendantz earlier this month, but sought out a second opinion from Yocum in hopes of getting better news. The 27-year-old right-hander has dealt with elbow issues in the past, straining ligaments on several occasions, but has never endured an injury of this severity.
Following a breakout season in 2011, Tomlin struggled out of the gate this season and never really recovered. The righty owns a 6.36 ERA, 4.9 K/9 and 2.2 BB/9 in twenty-one appearances this year.
Tomlin could return for the end of the 2013 season if he elects to pitch in relief, but will most likely be back for the start of the 2014 season.