The 27-year-old right-hander had been pitching with a damaged ulnar collateral ligament in his right elbow since 2014, when he was pitching for the Texas Rangers. He has been sidelined since March 17, when he experienced discomfort in his elbow while pitching in a spring training game.
Knebel was 4-3 with 16 saves and a 3.58 ERA in 57 games last season. He was outstanding in the playoffs, pitching nine games with a 0.90 ERA in 10 innings as the Brewers relied on a dominant bullpen to come within one win of the World Series.
Knebel had 39 saves and was a 2017 NL All-Star. "It happened five years ago and now it's just gotten a little worse," Knebel said. "I don't want it to really hurt me in the long run. Right now, I'm 27. I think it's better to do it now than wait until later."
The decision was left up to Knebel and he said it was a tough one, but he opted for the surgery rather than trying to rehab the injury and possibly being out a longer time or not knowing if the pain would return.
Orthopedist Neal ElAttrache will perform the surgery on Wednesday. "I've had the information now for a week and I couldn't just decide right away," Knebel said. "I hated that it was my decision. I really wish the doctor would have told me, 'Here's what we're doing.'
"As much as I want to pitch, it's going to be tough to just watch," he said. The Brewers beat St. Louis 5-4 Thursday in a season opener. Knebel said he would not be with the team this season but instead begin the healing process at the Brewers' training complex in Maryvale, Arizona.
"I've been reading a lot about everything and the success rate of Tommy John is very good," Knebel said. Knebel said he felt comfortable using ElAttrache, who did surgery on Brewers right-hander Jimmy Nelson last season.
"He did a great job with Jimmy's shoulder," Knebel said. Brewers manager Craig Counsell said he already knew Knebel would be out for an extended period, so the news did not change the team's bullpen plans.
"We fully support him making that decision," Counsell said. "Either way it was going to be a significant injury." Lefty Josh Hader remains a late-inning force for the Brewers, and he earned a two-inning save against the Cardinals in the opener.
Counsell said all eight of his relievers could close a game and he would not designate one or two pitchers for the role. Right-handed reliever Jeremy Jeffress is out with a right shoulder injury but is expected to return next month.
Counsell said Jeffress would pitch a spring training game on Saturday and would be on schedule to pitch in Arizona every three days. "That takes him to when the Triple-A season starts," said Counsell, who indicated Jeffress would pitch for San Antonio next Friday.
Nelson, one of the Brewers' top starting pitchers, is making progress in Arizona and should throw a bullpen session early next week, Counsell said. He is expected to pitch once or twice more in Arizona before joining Triple-A San Antonio.
"He does have to pile up some innings, just health and learning about himself," Counsell said. Nelson was injured while diving into first base in a game against the Chicago Cubs at Wrigley Field in 2017, and he missed all of the 2018 season.
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