Alexander, 31, joined Washington in mid-October, after being waived by Seattle in the offseason, to serve as a backup to Clinton Portis. Alexander played in four games, rushing 11 times for 24 yards and catching one pass.
He did not play Sunday against the Seahawks.
Alexander earned the NFL's MVP award after the 2005 season during which he rushed for 1,880 yards and 27 touchdowns. After leading Seattle to Super Bowl XL, Alexander suffered through two injury-plagued seasons, rushing for 1,612 yards and 11 touchdowns combined in 2006 and 2007.
Alexander, a former University of Alabama star, has been in the NFL for eight seasons. In that time, he has 100 rushing touchdowns, a 4.3 yards-per-carry average and 9,429 total rushing yards. He has 214 receptions for 1,511 yards and 12 TDs.
To fill the roster spot, the Redskins signed defensive tackle Ryan Boschetti.