Head coach Mike Shanahan delivered the injury report to the media on Monday afternoon.
So ends Barnett's first season in Washington after he signed with the team during training camp.
An 11-year veteran, Barnett entered 2013 having started all 139 of his career NFL games.
Credited by STATS, LLC with 1,026 tackles (722 solo), 42 passes defensed, 20.5 sacks, 12 interceptions (two returned for touchdowns), six fumbles forced and seven fumbles recovered through the 2012 season.
At the time of his signing, his addition gave the Redskins two of only three active players to be credited with 1,000-plus total tackles (
He was a key contributor on defense, often spelling Fletcher and allowing the Iron Man to continue his streak of consecutive games and starts.
He finished the season with 13 tackles on defense, one for a loss. He also contributed two tackles on special teams, playing in coverage for the first time since the start of his career.
Barnett is likely to be replaced internally by practice squad linebacker Will Compton, although the move has yet to be made official.