How Is Kemba Walker too Small to play in the NBA?

Notice how small that list is, and I don't think he has the wingspan of Rondo, nor the quickness and handles of Aaron Brooks or Chris Paul. However, I still believe he will be a successful guard but he will need to become a better pure shooter, he cant drive to the hole on big men like Dwight Howard, Andrew Bynum, Yao Ming (If healthy), and Tyson Chandler