Welcome to the 2014 version of Plugging the Holes, an eight-part examination from Football Outsiders of the biggest needs for every NFL team, division by division, going into the offseason.
In this edition, we look at the four NFC North teams.
Chicago Bears: Defensive line, linebacker
In the 10 years between 2003 and 2012, Chicago boasted a top-10 DVOA defense in seven seasons, a top-5 defense in five and led the league outright in DVOA twice. (DVOA is Football Outsiders' defense-adjusted value over average metric, explained here.)
The 2012 Bears defense led the league with a minus-26.8 percent DVOA, the team's best performance in our 25 years of data going back to 1989. (Better defense is negative, not positive, because it is preventing scoring.) Last year, the defense disintegrated. The 2013 Bears defense languished near the bottom of the league with an 8.6 percent DVOA, the team's worst performance in that 24-year span. After a 10-year reign of terror, and absent Lovie Smith and Brian Urlacher, the Monsters of the Midway were decisively vanquished.