The only mistake Chan made as a coach was selecting Edwards as a defensive coordinator. He needed to find a guy like him on the other side of the ball, a man capable of take lesser talent and put it in position to produce.
Every positive shown on offense, was negated by the ineptitude on defense. Even when the defense was forcing turnovers the sense of them breaking at the end was always latent. The offense had the confidence the defense never had and ultimately they cracked under the pressure to hold this team togheter.
Gailey is an excellent gameday coach, his clock management is almost flawless, the plays are given to the QB with plenty of time on the play clock. Sans a delay of game against the Patriots (2nd game) and the lackadaisical drive against the Titans I can't really remember a time where the offense was not in command of the situation.
Pre-snap penalties are way down compared with prevous coaching staffs. This is a great reflection of the coach.
Playcalling is subjective, when we were winning, Chan was great because he made adjustments and could made chicken salad out of chicken ****. I will never blame injuries (unless your franchise QB, that we don't have, goes down) I blame the losing streak more on the leadership of Fitz, or lack there of, rather than the guidance of their coach.
Can the playcalling get better? Sure, but it's easier to call a game without the pressure of scoring in every single drive to be alive in the score board.
If I'm the new Buffalo Bills onwer to be, I take note of the very positive things Chan have in his favor and see if with a little help from the benjamins can make him a winning coach in the NFL.