For any sport, to truly excel, you're going to need exceptional talent. And in most cases you'll also have to work hard. You're need both the nature and nurture. Look at all the supposedly "greats" in the past who have gone lauded in drafts or when they were in their teens only to turn out to be busts when they hit their professional careers.

In a case that hits close to home, you can't just hope to be a doctor without some natural inclination towards learning and some natural intelligence. You have to have a solid grasp of the sciences. Not everyone can do it. I've met many in my life who wanted to become a doctor but couldn't sweat the coursework. There's nothiing to be ashamed in that. But you can't just lean back on your natural gifts either. Medical school and residency are hard work and require long hours in the classroom, lab, clinic, hospital, and library. You're gonna have to read some large ass books and spend months on end studying for your licensing and board exams. You could be the smartest dude in the world, but you're still gonna have to get your study on.