Sources: Raiders keep Jason Tarver

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

The Raiders' defense improved from 29th overall in 2011 to 18th in 2012, Tarver's first season as defensive coordinator.

But Oakland slipped to 22nd in total defense this season, a year in which it allowed Philadelphia Eagles quarterback Nick Foles to tie an NFL record with seven touchdown passes and Kansas City Chiefs running back Jamaal Charles to catch eight passes for 195 yards and score five touchdowns.

According to a league source, three assistants from this season's staff will not be retained: defensive backs coaches Clayton Lopez and Johnnie Lynn and assistant special teams coach Keith Burns.

When the season ended, only offensive coordinator Greg Olson and linebackers coach Bob Sanders had contracts for 2014. Defensive line coach Terrell Williams, running backs coach Kelly Skipper and quarterbacks coach John DeFilippo agreed to one-year deals shortly thereafter, before assistant head coach/offensive line coach Tony Sparano received a two-year extension.

Receivers coach Ted Gilmore and tight ends coach Mark Hutson were expected to re-sign, though their futures, as well as that of senior offensive assistant Al Saunders, were not immediately known. Special teams coach Bobby April's agent, Frank Murtha, said April had yet to sign anything with the Raiders.