David Amerson and the Oakland Raiders have agreed upon a four-year extension worth as much as $38 million with nearly $18 million in guarantees.

The former North Carolina State cornerback was named Pro Football Focus' Most Improved Player in 2015, an award that factors in PFF's production grades throughout the season. The analytics site references that quarterbacks had a 140.2 rating when targeting Amerson in 2014, but in 2015, that number has dropped to 62.7.

A waiver-wire pickup in 2015, Amerson joined the Raiders after two seasons and two games with washington.