Heading into the 2015 offseason, the Chicago Bears made a clear effort to improve defensively, highlighted by the signing of outside linebacker Pernell McPhee. McPhee had impressed as a moveable pass-rusher early in his career in Baltimore, getting pressure both off the edge and from the interior. His success as an edge rusher continued in his first season in Chicago, racking up six sacks, 13 hits and 48 hurries.

With plenty of success coming from the McPhee signing, the Bears turned their attention to the defensive side of the ball in free agency this year. Two of the weaker parts of their defense in 2015 were at their two inside linebacker positions, where Christian Jones and Shea McClellin both graded negatively against the run, with McClellin also really struggling in coverage. For all the strength they had on the edge, the two weak links in the middle were an obvious issue.

They addressed this by adding two of the best inside linebackers available on the market in Jerrell Freeman (90.6) and Danny Trevathan (86.6). The pair had the fourth- and 10th-highest player grades among all linebackers last year, and will immediately turn a weakness into a big strength. Freeman's 97.9 run-defense rating was the best of any linebacker in the league, with the Indianapolis Colts defender making a tackle resulting in a defensive stop 12.8 percent of the time. Trevathan was good all-around, finishing the year as one of only seven linebackers with a grade of at least 80.0 both in run defense and in coverage.

Another area of need was on the defensive line, where rookie Eddie Goldman was the only player who really impressed in any form in 2015. The signing here was Akiem Hicks, who might not be a headline grabber, but he turned some heads in the second half of the season in New England. During a four-game stretch between Weeks 14 and 17, Hicks registered three sacks, three hits and six hurries on just 84 pass-rushing snaps. He's an upgrade at one 3-4 defensive end spot, and has the potential to be a low-risk, high-reward signing if some of his play for the Patriots was anything to go by.

They used two of their first three selections in the draft on the defensive side of the ball, adding Georgia outside linebacker Leonard Floyd and Florida defensive lineman Jonathan Bullard. Bullard has the chance to push for playing time early at the other defensive end spot, with Mitch Unrein his biggest competition for the role. He had the second-highest grade of any defensive tackle in all of college football last year, racking up seven sacks, six hits and 16 hurries, and figures to be an asset to the Bears defense.

Floyd is a good signing for a number of reasons. Only three edge defenders in the nation — and one in this draft class — had a higher overall grade than Floyd did in his final season at Georgia. He may have only had four sacks, but he added eight hits and 30 hurries. The addition of Floyd gives the Bears some flexibility, however, and if the way to slide Pernell McPhee down as an interior rusher in sub-packages, they can use Floyd and Willie Young, who had seven sacks, seven hits and 33 hurries a year ago, on the edge.

The rebuilding job isn't done yet, with holes remaining in the defensive backfield. Of all the starters on the Bears defense, the three lowest-rated at this point are cornerbacks Tracy Porter (50.5), Bryce Callahan (70.0) and safety Omar Bolden (52.1). They drafted rookie safeties Deon Bush and DeAndre Houston-Carson, and cornerback Deiondre' Hall in the fourth and sixth rounds, but how much they'll be able to contribute is a mystery at this point.

But while the Bears defense isn't quite there yet, they have taken another big stride forward this offseason, with several key additions that should help them in 2016 and beyond. They are absolutely a playoff-caliber defense heading into 2016, the only question will be whether QB Jay Cutler and a Bears offense that still has some weaknesses can hold up their end of the bargain.