Mengden underwent arthroscopic elbow surgery Monday, Mark Feinsand of MLB.com reports.
The procedure involved shaving off a small spur in Mengden's olecranon. A timeline for his return has yet to be announced. The righty is out of options and was likely on the roster bubble already after posting an uninspiring 4.83 ERA and a 16.2 percent strikeout rate in 59.2 innings last season.