Even if Spiller were not drafted, Jackson is the better back. The problem was drafting Spiller and generally drafting RBs too often in the first round rather than trading Lynch.
I don't think AJ left on good terms and I doubt Buddy Nix wants his old boss to come in and take all the credit if the Bills somehow turn things around.
I still maintain that the Bills are more aggressive at using the IR to create roster space than other teams. Players who might be out only 4-6 weeks seem to be put on there at times by the Bills because they want to add a player to the active roster for depth.