Cooper will undergo season-ending surgery to repair a partial UCL tear in his left elbow, Craig Mish of SportsGrid.com reports. He was transferred to the 60-day injured list Wednesday.
Cooper landed on the injured list July 19 with a sprained left elbow, and he'll opt to undergo surgery after being evaluated by multiple doctors. The procedure carries a 3-to-4 month recovery timeline, so he should be healthy for the start of spring training in February if all goes well in his recovery.