Backup Josh Johnson, who was signed on Wednesday and is the Redskins' fourth quarterback this season, replaced Sanchez. Alex Smith and Colt McCoy were both previously lost for the season due to broken legs.
Sanchez was abysmal in his first start for the Redskins, going 6-of-14 for 38 yards and two interceptions. He compiled a passer rating of 10.7 before being pulled.
The Redskins cited familiarity with their offense as the reason for signing Sanchez following Smith's injury.
Washington brought in Johnson after McCoy went down two weeks later. Johnson was the first overall pick by the San Diego Fleet of the Alliance of American Football league on Nov. 27.