The Tampa Bay Buccaneers have one of the most improved units in the NFL, according to Pro Football Focus. They ranked the Bucs' cornerback group as the fifth most improved unit this offseason. The team signed Brent Grimes, drafted Vernon Hargreaves and added Josh Robinson for good measure, while retaining Jude Adeji-Barimah, Johnthan Banks and Alterraun Verner. That's a pretty massive influx of talent.
First they brought in former Dolphin Brent Grimes, who was one of seven cornerbacks in 2015 with both four or more interceptions and seven or more passes defended. In the draft they added Vernon Hargreaves to play opposite of Grimes. For Florida in 2014, Hargreaves allowed an NFL passer rating of 41.6 when targeted, and he played at roughly the same level in 2015, with a passer rating allowed of 49.0. The Buccaneers should have more consistency and better play out of their cornerbacks this upcoming season.
The Bucs will be happy to hear it, but this is somewhat flimsy evidence. Brent Grimes played well last year, for the most part, but he's 33 and showed some signs of decline. And rookie cornerbacks almost always struggle. For this is one of the best improved units in the NFL, they'll need a lot more than Grimes and Hargreaves. Most notably, they'll need Alterraun Verner, who seems set to start on the outside, and Johnthan Banks to return to form. Both disappointed last season, but so did every cornerback not named Sterling Moore. The team is convinced that a new defensive scheme and new defensive backs coaches will help the veterans tremendously.
There is some reason to believe this. The Bucs allowed very few deep passes last season, the fewest in the league even, but opposing quarterbacks completed 70% of their throws against primarily underneath coverage. It's hard to do quite that poorly, and a lot of that had to do with what cornerbacks were asked to do: drop to specific spots, rely on inside help to stop slants and in general, allow short completions. That can be part of a successful defensive strategy, but it's going to make cornerbacks look bad and like they're not making plays -- simply because they're not really in position to do so.
It'll be curious to see how different Mike Smith's secondary will look. Fundamentally, it shouldn't be a shocking transition: Smith has mainly played fairly static 4-3 defenses, but he should be slightly more aggressive than Lovie Smith, especially on contesting shorter throws. That may also cost them more explosive plays, though, and whether the result will be worth the trade-off remains to be seen.