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.