2015 Rank: 16
2014 Rank: 2
Fall: 14 spots

With the way the Bills defense played in 2015, you would have thought it was Rob Ryan coaching them and not his twin brother, Rex. Sure, a 16th-place finish isn’t the end of the world, but this was just one season after finishing second without losing any major talent in free agency.

The run defense crumbled after Kyle Williams succumbed to injury and closed the season as the league’s worst of the year, although the pass defense managed a rank of 12th. Mario Williams has seen his effort called out, as he and Jerry Hughes each had only five sacks. By comparison, Williams, Hughes, and Marcell Dareus (two sacks in 2015) combined for 34.5 sacks in 2014.

Cornerbacks Stephon Gilmore and Ronald Darby were excellent in coverage, and the aptly-named nickel cornerback Nickell Robey was up-and-down playing mostly in the slot.