I would certainly sign him. At worse you get a guy who can fill in as a nice back up / nickel type player, or you may get a guy who may be able to still start and perhaps still dominate. Free safety is a very logical move, and as long as his health holds up could easily be among the league leaders in interceptions. Now if for some reason he really doesn't have anything left, I am sure that would be exposed during training camp and the team can simply release him at that point.