NEW YORK (CBSNewYork) — The mighty Yankees’ already-thin starting rotation received another blow Tuesday afternoon.

The team announced southpaw Jordan Montgomery is set to undergo season-ending Tommy John surgery.

The surgery will be performed by the Yankee’s team physician, Dr. Christopher Ahmad, at NewYork–Presbyterian Hospital on Thursday, according to the New York Post.

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After a quick hook following a seven-pitch first inning against the Houston Astros on May 1, the team announced they were placing the 25-year-old lefty on the ten-day disabled list with a left elbow strain.

Montgomery exited the second game of the four game series against Houston due to what he described as “elbow tightness” in his pitching arm.

At the time, skipper Aaron Boone said there was “nothing that would suggest” Montgomery would require the dreaded procedure. Given the typical Tommy John surgery rehab timetable, he will likely be sidelined until next year’s All-Star break.

Montgomery made his big league debut last season, going 9-7 with a 3.88 ERA in 29 starts and 155.1 innings while leading all rookie pitchers in WAR. Montgomery had a 3.62 ERA in six starts and 27 1/3 innings this season before his elbow started acting up.

With Montgomery sidelined, the Yankees have used rookie righty Domingo Germanas their fifth starter behind Luis SeverinoMasahiro TanakaCC Sabathia, and Sonny Gray. German has a 5.44 ERA in 41 1/3 total innings split between the rotation and the bullpen. Needless to say, the Yankees need another starter, and they did even before Montgomery got hurt.

Even with their rotation issues, the Yankees have the third best record (38-18) and fourth best run differential (+79) in baseball at the moment. Their rotation depth chart looks like this though:

  1. Luis Severino (amazing)
  2. Masahiro Tanaka (4.79 ERA)
  3. CC Sabathia (3.73 ERA)
  4. Sonny Gray (5.50 ERA)
  5. Jordan Montgomery (out with Tommy John surgery)
  6. Domingo German (5.44 ERA)
  7. Chance Adams (5.26 ERA in Triple-A)
  8. Justus Sheffield (3.80 ERA in Triple-A)

Not great. Adams had offseason surgery to remove bone chips from his elbow and he has not pitched well early this season, which is unfortunately for him (and the Yankees), because chances are he’d be in the rotation right now over German had he been performing. Sheffield just got to Triple-A and is the team’s best pitching prospect. They won’t rush him to MLB before he’s ready.

The trade market has not yet started to heat up but it should soon, once the annual amateur draft passes this week. Texas Rangers southpaw Cole Hamels is the top name on the pitcher trade market at the moment, though more names will join the mix before July 31. The Yankees were always going to be involved in the starting pitcher trade market. Montgomery’s elbow surgery means they’ll be that more aggressive.

The Yankees open a quick two-game series in Toronto Tuesday night, before traveling to Citi Field on Friday for a weekend series against the Mets.