I'd rock Portis (if he plays) and Coffee.
Portis, like Santana Moss, will have a big game eventually. This could be that game. The Bucs are going with an unproven QB and have a soft defense. Look for the Redskins to win the time of possession battle by a fairly large margin and take advantage of it by pounding the ball with Portis.
Coffee is in a great situation to succeed: he's on a run-oriented offense that is going to pound the ball no matter who is running, and they are playing the Rams. What's not to like about that?
Barber III is suffering from a quad injury. As a Steven Jackson dynasty owner, I remember seeing what quad injuries can do to good running backs. Be prepared to witness a decrease in power and burst until it is fully healed--something that takes quite a while. Choice will handle the load this week, anyway.
Of course if Portis doesn't play, you have to start Barber and hope for the best.