Chicago returns their entire secondary from last season, which is good news.
Off-season additions like Eddie Jackson and Prince Amukamara, coupled with breakout seasons from Kyle Fuller and Adrian Amos, helped construct a quality 2017 pass defense. The Bears were 7th in passing yards allowed, 15th in yards per attempt, and 5th in fewest touchdown passes given up.
But there is one area where improvement is desperately needed: interceptions. The Bears caught only 8 for the third year in a row in 2017. Only two NFL teams had fewer.
This has to change if the Bears want to become a good team. To understand why, let’s look at how important turnovers are to winning football games.
Turnovers & Winning Games
Over the last five years, there is a correlation of 0.50 between a team’s turnover differential and the number of wins for a given season. That means that roughly half of a team’s season outcome can be explained simply by looking at how many times their offense turned the ball over compared to how many times their defense took the ball away. Other studies have looked at this in greater detail and found the correlation to be somewhere between 40% and 65%.
I wanted to put this into a visual that’s a bit more concrete, so the table below shows how a team’s turnover differential corresponds to various season outcomes over the last 5 seasons (full data available here).
Teams that have a better turnover differential win more games and make the playoffs more often. It’s not a revolutionary idea, but I think it’s helpful to see some numbers.
Fumble Luck Doesn’t Last
So if the Bears want to improve, they need to improve their turnover differential. They actually weren’t awful last year (as I predicted before the season), as they had a differential of 0 by turning it over 22 times and forcing 22 turnovers, but that was with a hyper-conservative offense designed to limit turnovers.