Manning untradeable?

Drew Magary thinks that Peyton Manning is possibly untradeable and unsignable, leaving the Colts with no good option in 2012-13:

To say that Manning’s injury complicates his future is a mild understatement. It virtually guarantees his release from the Colts, since the Colts will have to draft Andrew Luck and will be unwilling to restructure Manning’s contract if they know he’s not guaranteed to play next season. That’s too much salary cap space devoted to one position, with the real risk of Manning’s cap number going toward another wasted year. And certainly, there’s no way the Colts will be able to trade Manning, not with the cap implications, and not with other teams fearful of trading for damaged goods.