Reddick suffered a sprained MCL in practice on Friday, Ian Rapoport of NFL Network reports.
It was a rough day for linebackers at Bills' training camp Friday, as both Reddick and second-round draft pick Reggie Ragland (knee) went down with injuries. The 26-year-old Reddick will likely miss around six weeks, which could jeopardize his chances of landing a spot on the 53-man roster.