Staley can't do it by himself either, IMO.
But Cowher knows how to use the two of them together. Bettis has been getting the ball in first and goal situations, and has been very effective.
Duce is smaller, but is more effective for short passes and running outside.
IMO, when Duce comes back, Cowher should keep using Bettis as primary back. Jerome has earned it.
You guys are forgetting about Verron Haynes who is a great change of pace for the other two. And also Willie Parker could provide some key plays in the last few games as he runs a 40 in 4.2 seconds and is probable the best back we have to get it outside. I admit to being down on the Bus the last year or so and right now I'm thinking he's somehow linked to BALCO. HE'S BEEN RUNNING WILD!