Akrasian thinking we don't have room:
And Mathis wants to be paid like an elite player despite most teams having spent their cap space already, and his age, and his having been injured part of the season, and prospering in a system that about half the teams run. He makes sense for some teams, I suppose - the Broncos know they are screwed once Peyton retires, so they need to go for it now and can defer the cap hit until Peyton's salary hit is gone also. The Rams need to keep cap space to re-sign more of their young players, run the wrong system, and have more young OL they will want to keep than there is space on the roster.