The NFL's most improved units

The Tampa Bay Buccaneers' secondary should be much improved with Darrelle Revis. AP Photo/Chris O'Meara

The goal for every NFL team is to use the offseason to upgrade positions of weakness. Some teams do this through the draft, while others are more inclined to use free agency to fill areas of need -- all with varying degrees of success.

I went back to the film room and reviewed the draft and free-agent acquisitions to see which teams improved the most this offseason. Below are eight NFL units that weren't necessarily elite in 2012, but should be much better this coming season.

We start off with a team that made one of the biggest offseason acquisitions in recent memory, bolstering a position group that was one of the league's worst last season.

Tampa Bay Buccaneers secondary

The Bucs not only made significant changes in personnel this offseason, but they also are making the transition from a Cover 2 look to a physical man scheme, and big improvement is expected in 2013. It all starts with Darrelle Revis, who changes this entire defense if he can successfully come back from an ACL injury. The Bucs drafted fellow CB Johnthan Banks in the second round to team with Revis, and added outstanding free-agent safety Dashon Goldson from San Francisco to play alongside the outstanding youngster Mark Barron.