Do we all forget how poorly Seattle plays away from home?
The Rams handled them last weekend with a nonexistant offense and the Redskins serviceable defense and strong running game is enough here.
They lost at Detroit, lost at St. Louis, lost at Miami. They generally seem to have problems with teams they can't outphysical at the line of scrimmage. Their corners will cause the quarterback to hold on to the ball, but if the line can deal with their pass rush they are more of a good defense not "great".
Their party is over after their run, Redskins are too physical and RG3 and Morris will keep the ball in their possession.