Posterior cruciate ligament: Merriman suffered this tear, which he has classified as a grade three, the worst it can be, in his second NFL game. It happened while he was running down to cover the opening kickoff in an exhibition game Aug. 26, 2005, at Minnesota. Players have played their entire careers with this injury. The PCL provides front-to-back stability.

Lateral collateral ligament: This injury happened Dec. 9 at Tennessee and became an immediate source of friction. At the time, Merriman called the hit by Kevin Mawae and David Stewart a “cheap shot,” and game tape made it appear so. In fact, the league fined Mawae and Stewart. The severity of Merriman's LCL tear is unknown, but with a tear of any degree Merriman will experience side-to-side instability.

– KEVIN ACEE