To address youre last sebtence first, stones was brought up from the u21s to start reguarly was he not? or galloway, he has played a fair few. So that's that
There's very few managers in the league that would've first given the chance and secondly persisted with a young ball playing center half in such a high pressure league. Can't argue the fact that bobby did great getting him involved and the big reason for John bursting onto the scene is the persistence to stick with him even after costly mistakes.
And as for moyes, as he shown with Barkley, one mistake and John would've been shipped off out on loan or back to reserves, that's if he even got a chance to begin with. His reluctance to give young defenders a shot unless absolutely last resort eg. Duffy, is simple fact.