There was already a lot of chaos in that building. Now the Interim HC has made more by giving control to someone else. The QB is a friend of the OC whose play calling duties were stripped off from him. It will be hard to see who is calling the shots in that building. The Bills will have to leverage this and come with their gun's blazing. McDermott is a better coach and he should have his team prepared for this moment.
Also, the Bills have their own ghosts to clear up...their QB went 9 for 30, one of the worst performance as a QB in the league over 30 years....I am sure he wants to correct that blemish on his career.