According to the National Football Post, former Bengals OLB Keith Rivers filed a grievance against the Bengals last season in a dispute over being placed on the non-football injury list as a result of his wrist-surgery which cost him the entire 2011 season:
There was a story behind the story on the Keith Rivers trade to the Giants. The former first round pick had surgery on his wrist near the end of the lockout last summer. The Bengals thought he could have had it earlier in the offseason, and did not approve. The team subsequently put him on the non football injury list. Rivers wanted to be put on the physically unable to perform list, which would have enabled him to collect his salary. He filed a grievance against the team. There were hard feelings, and both sides thought a fresh start was in order.