Whoever the next d coordinator is, he will promise to deliver an "aggressive, attacking, hold-no-prisoners" style of defense. You know, just like Wade did, and just like Ryan did, and ...
He can still win games just by throwing the ball and handing off to Morris, but yeah, if defenses don't have to fear him running, that's a big advantage.
Norv would be insane to sign up for a potential lame duck Garrett season, and then be at the mercy of the new coach in 2014. Nor do we want a situation where the new coach has to accept Norv as OC.