Cotham went out on a rehab assignment and pitched on June 30 for Double-A Pensacola. He faced four batters before he felt soreness in his knee. Following a break, he pitched one inning for Pensacola on July 16 and hasn't played since.
The Reds acquired Cotham and three other players in the December trade that sent closer Aroldis Chapman to the Yankees.
In other injury news, Reds pitcher Alfredo Simon (strained right trapezius) threw a bullpen session without issue on Friday and was scheduled to throw another 40-pitch session on Sunday. Simon has been out since last pitching on June 15.
Reliever A.J. Morris (right shoulder inflammation) was also scheduled to throw a 40-pitch bullpen session on Sunday.
Mark Sheldon has covered the Reds for MLB.com since 2006, and previously covered the Twins from 2001-05. Follow him on Twitter @m_sheldon and Facebook and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.