Why is the relationship between "genius and drill," as emerson explains it, paradoxical (para. 3) ?

When we consider someone as being a genius, we have the idea that this person has a superior intelligence and is very good at perfoming some tasks, and the fact that they still need to practice and exercise regularly may seem a paradox. But the genius is only the inicial part, which needs to be followed by the drill in order to attain excellence.