I think Ferentz is a motivator. There may be a lot of things he's not good at, but I have to think that taking a smaller, lesser known program like Iowa and not having a losing season in a decade, with 2 BCS bowl appearances means he's good at motivating his players.
Take a look at Angerer. He wanted to quit. Now maybe Ferentz didn't have much to do with his return, but maybe it did. Look at Greene. Again outside influence, or Ferentz influence? There's a lot of guys that step up like that. Guys you wouldn't expect much from, that don't have amazing natural talent, but can perform on the field. Adam Robinson is another example.
I'd like to think that Ferentz will have a talk with CJ and either motivate him to become a great player, or he'll disappear. Either way the team should be better for it.