I don't know about going game by game because during McD's tenure the Bills usually play close games regardless of competition. And they win their fair share of them. Ugly or not, they win some. The KC game is a perfect example of that. Even though KC clearly outplayed the Bills, they were still in that game late, and a break or two their way...they win it.
I'm VERY concerned about this Defense. And I don't see a ton of improvement coming from that side of the ball the rest of the year. The Bills issues on Defense are, to a large part, personnel related...However...If they only improve on the 3rd and long situations, where they have been terrible all year, it will result in overall team improvement IMHO...
On the Offensive side I think it's a little more on Daboll. Most of the Bills issues on Offense so far are self inflicted. And it starts with the scheme and play calling...The talent is there. 2 plays yesterday showed how the Bills are clearly not taking advantage of their strengths enough, and those were the catch and runs by Diggs and Brown. The ball to Diggs was about 10 yards past the line...The pass to Brown was very close to the line of scrimmage. These are easy tosses for Josh that turned into BIG results. The Bills need more of that on Offense. I think the running game will continue to improve now that Mongo is back...
The other factor, like it or not, is that the Bills have REALLY suffered from the lack of the 12th Man at Home. Yes...It has exposed them a bit as being a rung below the real NFL contenders, because a real contender would not need the Home crowd as much. But this team would have already had much better "style-point" victories vs. the Rams, Jets, and Pats with a sold out crowd at Home and I have zero doubt about that...So if any of these Home games down the stretch are played in front of a crowd you will see the Bills elevate their game. 😎