Yankees right-hander Chase Whitley will undergo Tommy John surgery tomorrow, reports Ken Rosenthal of FOX Sports (on Twitter). Whitley had previously been diagnosed with a partially torn ulnar collateral ligament in his right elbow, but the team was said at the time to be weighing its options.

Other injuries on the Yankees roster led the 25-year-old Whitley to the team’s rotation, and he pitched reasonably well in four starts, tallying a 4.19 ERA with 7.4 K/9 and 2.3 BB/9 in 19 1/3 innings before succumbing to the injury. Whitley reportedly did not speak up about the pain in his elbow after initially feeling it, and the stats seem to bear that out. He allowed just one run in 12 innings in his first two starts before being torched for eight runs over his next 7 1/3 innings. Whitley’s final outing last just 1 2/3 innings. Surgery will likely keep him on the shelf through mid-summer 2016.

The Yankees are known to be thin on pitching depth as is, with Ivan Nova currently rehabbing from his own Tommy John (which he underwent in 2014) and Masahiro Tanaka currently on the DL, trying to avoid the same fate. Michael Pineda looks the part of a true No. 1 starter this season, but he’s had significant shoulder injuries in the past, so it remains to be seen if he can handle a full season’s worth of innings. CC Sabathia has been better than 2014 but still sports a 4.67 ERA, while trade acquisition Nathan Eovaldi has been serviceable, though not spectacular. Adam Warren has also struggled to an extent, and Chris Capuano’s first start after opening the year on the disabled list did not go well.

The Yankees, then, may miss Whitley more than most would assume based on his limited track record. If nothing else, his absence thins out the teams depth and leaves them much more susceptible to additional injuries in the rotation, as the club’s Triple-A rotation is lacking in high-upside arms.