 On April 8 , 2015 , Nathan was placed on the 15 @-@ day disabled list due to a strained right elbow . During a rehab start with the Toledo <unk> <unk> on April 22 , Nathan re @-@ injured his elbow after throwing only 10 pitches . The same night , Nathan underwent <unk> , which tested positive revealing tears in his ulnar collateral ligament of the elbow and his <unk> <unk> muscle , and would undergo Tommy John surgery , ending Nathan 's 2015 season . Sources projected that this surgery could end Nathan 's career , but he was not planning to retire yet . 
