The Yankees placed Whitley on the 15-day disabled list last Friday with a right elbow sprain after he exited his Thursday start in the second inning. CBSSports's Jon Heyman then reported that an initial diagnosis suggested Whitley tore his UCL and could require Tommy John surgery.
Whitley opted for the surgery after meeting with New York's team physician. He will have the surgery on Tuesday.
"It's extremely disappointing, because this kid's done everything that we've asked," Yankees manager Joe Girardi said.
The 25-year-old gave up nine earned runs in 19 1/3 innings and struck out 16 this season. He was 4–3 with a 5.23 ERA in 24 games in 2014.
New York (22–17) plays the Nationals in Washington on Tuesday.
- Molly Geary