In 2015, we saw something we never expected: the defense became the strength of the team.
This was at least in part due to the failings of the offensive side of the ball, but this oft-maligned unit actually became a pretty decent group.
They sat around the outskirts of the top-10 units in the league for most of the year, were one of the better groups in terms of sacks despite their best pass rusher playing at ILB (43; tied for seventh league-wide), and had a very impressive young secondary playing well on most occasions. This helped keep the team in all but a couple of their losses (at Denver, at Arizona).