And just to add to that post, there are a handful of athletic skills that are vital to just about any sport: strength, balance, vision, agility, speed, and stamina. Instincts come with familiarity, I would say. If you have those skills and spend a better part of your life dedicated to playing one specific sport, chances are you're going to be pretty damn good.
Take a guy like Kobe, for example. He's got all of those attributes, and he certainly has the work ethic and desire to win. Unless he's running on two left feet, which I doubt, there's no way he wouldn't have been a successful soccer player if he had dedicated his life to it.
Conversely, Michael Essien would probably make a hell of an American football player.