This will be an interesting game because it is two of the top offenses and some serious running power. Seattle has the edge on defense although the Redskins have clearly improved on D since the bye week.
		
		
	 
Since the BYE, comparing yards given up by Washington against the full season team defense rankings on a yards/game basis

assing Yards per game given up: 273.4 (30th)
Rushing Yards per game given up: 96.6 (7th)
Overall: Yards per game given up: 370 (25th)
When people point out that Washington has a strong run defense, could it be the case that their secondary is so soft that teams do not need to run against them?
Now granted over the course of this season Seattle was 27th in Passing offense and 3rd in Rushing offense so a better question is how did 
Washington's Rush Defense fare (after the BYE) against teams with strong rushing offenses?
Sorted by team offense rushing rank in yards per game
Rushing Yards given up in each of their 7 games after the bye:
186	yards	Ravens	11th (home)
80	yards	Eagles	13th (home)
100	yards	Eagles	13th
117	yards	Giants	14th (home)
58	yards	Browns	24th
35	yards	Cowboys	31st
100	yards	Cowboys	31st (home)
Doesn't seem like their rush defense is that dominant this season after the bye particularly since they did not face any teams with elite rushing offenses and got to face the Cowboys twice along with the Browns.
Now let's look at 
Seattle's Rush Offense and see how they did, will just look at their performances after their bye in week 11
176	yards	49ers	4th
176	yards	Bears	8th	(away)
96	yards	Dolphins	13th	(away)
153	yards	Rams	15th
284	yards	Cardinals	28th
270	yards	Bills	31st	(away)
While it is clear Seattle absolutely decimates teams with very bad run defenses (Arizona/Buffalo), they are still putting up elite (rank=1 if averaged over a season) rushing stats against very good run defenses such as San Fran and Chicago.  Plus San Fran and Chicago are legit "good run defense" teams since their pass defense rankings are 4th and 8th respectively.
I'd expect to see Seattle run all over Washington at FedEx, I think it is safe to predict a minimum of 150 total rushing yards which is the equivalent of a top 5 rushing offensive performance (averaged over a full season).