Njoku (undisclosed) is working on a side field with the rehab group at Monday's practice, Scott Petrak of the Elyria Chronicle-Telegram reports.
This is the first report of any injury for Cleveland's starting tight end. The team has been shorthanded at the position, with Demetrius Harris and Seth DeValve both recovering from concussions during the early portion of training camp, so a lengthy absence by Njoku could have the Browns scrounging through the free-agent pool for depth.