The Oakland Raiders have re-signed defensive coordinator Jason Tarver on the day his contract expired, according to reports.

Tarver improved the Raiders' defence from 29th overall to 18th in his first season in charge, but last year they slipped to 22nd as they recorded just four wins all season.

Oakland allowed two opposing quarterbacks to post perfect passer ratings this season, with Nick Foles throwing for seven touchdowns in a match against the Philadelphia Eagles and the Kansas City Chiefs' Alex Smith throwing for five in December.

However, the Raiders have decided to retain Tarver alongside Terrell Williams, Kelly Skipper and John DeFilippo, all of whom have signed contracts since the end of the regular season.

Defensive backs coaches Clayton Lopez and Johnnie Lynn are not expected to be re-signed, while assistant special teams coach Keith Burns will also not return next season, according to a league source.