It's not just physical either though. Football is to me, the most challenging game to learn to become a pro. There is a reason there are so many coaches on every team to teach the game. It's so detailed, and so fine tuned at the pro level, a kid from high school has no chance to come into the NFL and succeed. He would get abused in a second even if strong enough. You really think a WR can come from High school, where he was faster, quicker, better at everything than the guys he played...and face a pro CB? He'd have zero shot. He wouldn't have the 100 hours of learning how to get off a press, the 100's of hours learning how to read the option route based on what the defensive is giving and the routes others are taking. And that's just two things he hasn't learned at an advanced level. If if he somehow knew those, there are 40 other things he needs to perfect. Basketball is challenging as well sure, but it's not nearly as detailed as football.