Mangini and Daboll are just space retainers and scapegoats for season one of the Holmgren era in Cleveland. Once Mike evaluates the roster and gets a couple of offseasons of his system personnel in place via FA, draft and trade, he will choose a new HC to fit his scheme and that guy will bring coordinators in who suit him... No sense giving the Dawg Pound a season to build frustration with his own guys when he has scapegoats available that his boss was going to have to compensate either way...
Josh who is still installing this offense in Denver, Pioli and Charlie who have a QB who played with him, and even Dimitroff whose young QB is depending on an aging elite TE in their offense had no interest in a guy drafted and developed on their watches. He simply was never a great fit for this scheme. Too complicated and functioning within it sapped whatever natural ability he may have had. He was always at least slightly out of place as a rookie, but he could still do damage when Brady did locate him. He used to run over people with abandon when he did catch a ball. That evaporated as he struggled to master all the nuances this system demands. He was always forced to overthink because it didn't come to him instinctively. A guy like Welker on the other hand was just born getting it... We need more guys like that because they maximize our QB's best attributes.