The Tampa Bay Buccaneers had an average season defensively in 2013. They weren't anything special and weren't terrible. However, with the talent they have on the defensive side of the ball (their defensive line might be the best defensive front four in the NFL) already for this upcoming season, they should be decidedly better in 2014.
New Starter: Alterraun Verner
Although Verner is a downgrade from Darrelle Revis (who isn't besides Richard Sherman), the difference isn't substantial. Verner is an excellent cover guy who is reliable against the run. He's small in stature but tackles with excellent form. Him and Jonathan Banks will make an excellent cornerback pairing for many years to come.
Area of Improvement
What they need to focus on more is stopping the run. In bother categories, running and passing, their defense was just about right in the middle of the pack. However, the one position group most in need of improvement is their linebacker corps. Outside of Lavonte David, they don't have a starting caliber linebacker. This is something they could easily address in this draft and I fully expect them to.
Potential Breakout Star: Lavonte David
If he hasn't already broken out as a star, look for him to do so this year. David made a case last season to be one of the top outside linebackers in the league and this year he will be looking to solidify that claim. David has great speed from the backside of the play and his athleticism allows him to be one of the better coverage linebackers. As far as 4-3 outside linebackers go, I expect David to make a strong case of being the best in the league when this season is all said and done.
On His Way Out: Mason Foster
Foster doesn't have much of a future in a Lovie Smith system if he continues down the path he's headed. He's extremely aggressive and can't get off blocks very easily because of his lack of size. I expect the Buccaneers to draft someone to give Foster some competition during training camp and how he responds to that competition could decide his fate in Tampa.