This is going to probably be a super unpopular opinion but I think losing Lee Smith has hurt the offense and locker room.
I am not saying he is only difference between 10-2 and 7-5, but him being TE #2 I think would have helped our run game, our red zone offense, and like I said locker room. He is a gritty guy. I think if he is on the team, the Bills probably would at least be 8-4. (His blocking helps create a few more yards running, during a drive) (Maybe instead of a run on first & goal its a PA easy flip to Lee Smith, he bobbles it a little 😉, but still catches it TD!)
EDIT: Our passing game too (thinking more along the lines of pass blocking though)