I think it has a lot to do with his conditioning. Although still not quite the fitness level his fans or himself would like to have, he has improved a lot over last season. I remebred he was struggling last year around the same time. He uses a lot of engery to set picks for Steve, Cat and Jackson. It seems like that every time houston is stagnent on offense, Yao ming would set up a pick and roll to the basket. 8 out of 10 times ends up with one of the guards throwing up bricks, while he did not get to touch the ball. But I think this kind of situation will change gradually and he eventully will become the go-to guy at crunch time.