3. Rex Ryan (2015-2016)
The biggest splash hire the Buffalo Bills have made since 2001 was when they named Rex Ryan their head coach ahead of the 2015 season. Ryan had great success with the New York Jets with four of his six seasons finishing with eight or more wins.
Ryan also would reach the AFC Championship Game twice during that time but would not be able to get over that final hurdle and reach the Super Bowl.
The Buffalo Bills hired Rex Ryan due to his defensive knowledge and experience but the defense never really developed into one of the best in the league. In the two seasons in Buffalo, the Bills would finish 19th in yards allowed each season but did a great job running the ball as they finished first in rushing yards each year.
The Bills would fire Rex Ryan before he could complete his second season and it was a notable shift in the team's philosophy in how to try and fix the franchise.