The Redskins' most energetic locker room presence for the past five years, Washington made the Pro Bowl following the 2004 season, his first with the team, but hamstring and ankle injuries eventually took their toll on the 31-year-old star.
Washington missed four games in 2007, six in 2008 and often played hurt. He had no sacks last season for the first time in his nine-year NFL career.
The Redskins, as they do every February, have been restructuring contracts and considering which players to cut to clear salary cap space for the start of free agency next week. Other high-priced players who could be released include defensive end Jason Taylor and cornerback Shawn Springs.
"As free agency approaches there are difficult choices that have to be made," coach Jim Zorn said. "This certainly was a hard decision because Marcus played such an important role on our defense and in our locker room."
The Redskins will "try to be active" in free agency, Zorn said this week at the NFL combine. The team made no high-impact signings last year, a change in tactic from the huge spending sprees of earlier in the decade.