People have this romantic notion of the Bills 2014 defense. Please folks, (if you are thinking Pettine's loss will be difficult to overcome) go look at last season. Yes, the defense go sacks, but at what expense? How good were they really?
I don't know whether Schwartz will field a better defense (based on personnel/scheme), frankly, I'm skeptical (but also hopeful). But, if you are sitting in your home pining for the "Pettine years" I'd ask you to reconsider.