Look at this way. When your opponent shot a ball back to you, the ball bounce higher after hit the clay than the fast ground such as grass and hard surface. In this case give you more time chase the ball. Basically that is why Nadal got more benefits from “green clay”. He chases very ball; that is the style of the clay player.

In the other hand, fast surface player usually not trained this way. They do not chase the ball at same point, not because they are lazy or easier giving up. Their instinct tells them not to, after all years of training and practice.