Jeremy Hefner will almost certainly undergo Tommy John surgery to replace a torn MCL in his right elbow.
"I think I expected it a lot more than I was leading on," Hefner said. "I was trying to pitch through it. I was trying to make it to the end of the year."
Hefner will also have a sizeable bone spur and several loose bodies removed from the same elbow.
The 27-year-old is 4-8 with a 4.34 ERA and 99 strikeouts in more than 130 innings this season.