The move is the latest to distance the organization from the era of late owner Al Davis. Kelly originally signed with Oakland as an undrafted free agent in 2004 and quickly became a mainstay on the defense, signing a $50.1 million, seven-year contract to remain with Oakland in 2008.
But general manager Reggie McKenzie cut Kelly two years before the end of that contract, getting Kelly's $6.5 million salary for 2013 off the books.
Kelly, 32, is the third prominent player acquired by Davis who has been released this month, following defensive back Michael Huff and receiver Darrius Heyward-Bey.
Punter Shane Lechler, safety Mike Mitchell, tight end Brandon Myers, defensive end Matt Shaughnessy and defensive tackle Desmond Bryant have also all left as free agents. Only 18 players who were part of the organization when Davis died Oct. 8, 2011, are still on the roster.
Running back Darren McFadden and safety Tyvon Branch are now the longest-tenured position players on the roster, having been drafted in 2008. Long snapper Jon Condo joined the team the previous season and kicker Sebastian Janikowski was a first-round pick in 2000.
Kelly started all 80 games for Oakland over the past five seasons. His best years came in 2010 and '11 when he teamed with Richard Seymour to form a formidable force in the middle of the defensive line. Kelly had 14½ sacks over those two seasons and was one of the better pass-rushing tackles in the league.
But he struggled to get to the quarterback last season, recording just one sack in 16 games. He also had only 18 quarterback pressures, according to Pro Football Focus, down from an average of more than 30 the previous two years.
The Raiders are completely reworking their defensive line, having lost Shaughnessy and Bryant to free agency and with no interest in bringing back Seymour as a free agent. Defensive end Lamarr Houston is the only returning starter.
McKenzie has signed Jason Hunter, Pat Sims and Vance Walker this month and could use the No. 3 overall pick in April's draft to add another lineman.
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