I can see Coach being a bit nervous and possibly second guessing himself. yes he knows the Pats as well as anyone, but it cuts both ways. Josh is a stand up guy, loves Brady and Cassell, and has a lot of respect for the Pta's organization. He may have a mental hurdle to get over in order to be able to gameplan against his old team.
Unlike Manchild who was a reviled D bag that had more of a revenge fantasy from his feeling of not being liked because he was such a cocky pr_ck.