Problem w/ my running back- mental?

The boy we are projecting at running back is approx. 220lbs 6'0 tall and runs about 4.7. The problem is he runs like he is 125lbs and wears a skirt. He chops his feet when he gets close to traffic instead of using his weight to bowl forward and wants to run more like a Barry Sanders than a Bettis. We are a gun team, running primarly I.Zone, Ctr, Power, & Spd. Option, with our main emphasis on the zone. He is also a little stiff in the hips and not quite as smooth as I would like on the cutback. My question, is there anyway to break him of these habits. I don't know if it is a mental block or what. I have had him for 2 years now, running the same drills as the starters before him and he hasn't changed much. He has to be able to run hard or he is a waste for us at the position. Would be grateful for any ideas.