I would say Bush, Torain then Crabtree.
Always play the primary RB over a WR2 every sunday. Bush is going to be solid, and I dont think McFadden has much to do of anything, so no worries on a 80+ yd w/ TD game for Bush.
Torain will be similar stats but Redskins can get behind early and really limit Torains production if McNabb is tossing the ball alot. Bush is Safe. Crabtree is OK, but a mid WR2 and not playable over said RBs. Let him prove it 1 or 2 more weeks before you play him every week. I have both Bush & Crabtree, not bad at the moment.