Lefthander Ryan O'Rourke has a partially torn ulnar collateral ligament in his elbow and will need Tommy John surgery, the Twins announced today.

O'Rourke traveled with the Twins to Arlington to be evaluated by Rangers orthopedist Dr. Keith Miester. After Miester consulted with Twins doctors, it has been determined that O'Rourke needs season-ending surgery.

O'Rourke ruled out any chance of a modified procedure that would allow him to return to action sooner. He's looking at a return to action in early 2018.

"If I could put a two month timeline on it, I would say that," O'Rourke said. "There's reality, and it is a lot longer than that."

He was diagnosed with a strained flexor pronator mass near his elbow during spring training. An MRI exam revealed no structural damage, so O'Rourke started a throwing program. Discomfort persisted, forcing O'Rourke to seek a second opinion. A second MRI exam was taken, which also came back clean.

"But what we delved into deeper, it made complete sense," O'Rourke said. "I think my arm has been through a lot in 28 years of throwing."

O'Rourke is in the process of selecting a surgeon for the procedure.

As for the game, Ervin Santana will attempt to improve to 4-0 on the season while the Twins try to win a second game in Arlington. Santana has not pitched here since 2013, when he gave up just one unearned run over seven innings while pitching for Kansas City.

Twins manager Paul Molitor admitted it was hard to leave Robbie Grossman out of the lineup, but this is the result of Kennys Vargas being called up and needing at bats. So the American League leader in on base percentage is not in the lineup tonight.

Twins

Brian Dozier, 2B
Max Kepler, RF
Miguel Sano, 3B
Joe Mauer, 1B
Jorge Polanco, SS
Jason Castro, C
Kennys Vargas, DH
Eddie Rosario, LF
Byron Buxton, CF

Ervin Santana, RHP 6-7, 6.93 ERA at Globe Life Park, but gave up unearned run in last outing here on June 2, 2013 while with Kansas City.


Rangers

Shin-Soo Choo, DH
Carlos Gomez, CF
Nomar Mazara, RF
Mike Napoli, 1B
Rougned Odor, 2B
Elvis Andrus, SS
Joey Gallo, 3B
Jonathan Lucroy, C
Ryan Rua, LF

Andrew Cashner, RHP