He's some who needs to get in rhythm to be successful, meaning he needs to be the a larger share of carries. That's obviously not going to happen here, but when you look at his stats he did most of his damage after Blake got hurt. He's also not a great fit for Michigan's scheme which is more north/south, he needs to get to the edge and be in space. The final issue, is they don't throw enough to their running backs (see Chris Evans). As a true freshman Donovan went off against Maryland but he hasn't had that type of usage since.
I think people are forgetting Michigan is a ball control offense. Washington can't score if they don't have the ball. Taking time off the clock with long drives means less opportunities and a fresher defense. I think Washington's defense is the x-factor in this. If they can get turnovers or make Michigan a passing team, then they have a great chance to win.