I think Jamie Carragher has been a great player.
Not in the top bracket of PL defenders, but probably the category just below. He's definitely not someone you'd have been disappointed to sign. He's old school, body on the line, which is dying out in modern football. Fair play to him on calling it quits rather than playing on.
I'll put money on him ending up a manager at some PL club in a few years. The guy is supposed to be a walking encyclopedia of football knowledge. He'll watch ANY game that's on TV and knows most players across the major European leagues. That alone gives him a head start on most PL managers who only know how to work the old boys network.
Although, counting against him is the fact he can only speak broad Scouse and therefore most people can't understand a ****ing word he says!