15. Chicago Bears The Chicago defensive line last year may have been one of the worst units in football. It was a disaster that only became worse as injuries bit, forcing defensive end Corey Wootton inside to play as an every down 3-technique defensive tackle. The good news is the team saw the problem and aggressively sought to fix it this offseason, bringing in upgrades in the form of Lamarr Houston,Willie Young and Jared Allen. Not content with that, they also spent draft picks in the second and third rounds on the line. The secondary should be boosted by Charles Tillman being back 100 percent healthy, but they also planned for the future by draftingKyle Fuller in the first round. Linebacker remains the biggest problem on defense, with Shea McClellin trying to transition to a completely different role and Lance Briggstrying to hold things down virtually on his own. By the numbers: Despite the additions on defense, seven of the starters are graded as average or worse (58.3 percent), with rookie Fuller an unknown quantity. On offense, Brandon Marshall is the lone blue-chip player, but receiving partner Alshon Jeffery is hot on his heels as a high-quality player.