Does it also not reveal that he's assigned the weaker offensive player? A big in this league needs to be able to offer help to be worth all that much on that end. Tim Duncan didn't stop Shaq all that much, but he scored on him, and helped to stop anybody but Shaq.
Bargnani has some tools. He just doesn't react well. He sometimes works best while guarding a pg with the ball, because he can play so far off a small and not need to react so quickly, and also be able to recover with his length. If he's got good position on any guy with the ball, he's miles ahead of any other time when he struggles with positioning and seeing both his man and the ball. But in a fluid game it's tough to maximize on the number of those occasions. Casey did a nice job of simplifying his movements and making his job less about reacting and just trying to minimize positioning problems. The question will be how far the team can go with that.