Cubs right-hander Ethan Roberts will require season-ending Tommy John surgery after sustaining a right elbow injury during his rehabilitation appearance Sunday at Triple-A Iowa, the Chicago Tribune reported.
Roberts previously was placed on the 60-day injured list. He last pitched for the Cubs on April 29.
The 24-year-old Roberts exited after facing just one hitter at Iowa.
Roberts owns an 0-1 record with an 8.22 ERA in nine relief appearances this season.