The Guardians estimate the 28-year-old Stephan will be sidelined at least one year and up to 16 months.
Stephan has appeared in 137 games the past two years, used primarily as a set-up man for closer Emmanuel Clase. Stephan did not pitch at all during spring training with a bone bruise, and tests revealed he needed surgery.
Stephan went 7-7 with a 4.06 ERA and two saves in 71 games last season. He's 16-13 with a 3.73 ERA in 180 games the past three years.
His loss is another blow to a Cleveland bullpen dealing with numerous injuries. Right-handers James Karinchak (shoulder), Ben Lively (viral illness), Xzavion Curry (viral illness) and lefty Sam Hentges (middle finger) all started the season on the 15-day injured list.
The Guardians are also without starter Gavin Williams due to right elbow inflammation.
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AP MLB: https://apnews.com/hub/mlb