On the other hand, I can’t imagine the guys that ended up being cornerbacks, wide receivers, safeties, or even halfbacks couldn’t have become soccer professionals given the right culture, training, and desire growing up. Sure, linemen, tight ends, and fullbacks aren’t built for soccer.
When we are talking about the really TOP elite of football those kids get into it at age 5. From that age on every day consists of hours of football. There are scouts looking at prepubescent kids all over the world ready to sign them.
In a hypothetical world where every kid plays only soccer, every potentially great soccer player has been practicing the sport from an early age. In a world with 10 competing sports, some potentially great soccer players might have be playing baseball or basketball from a young age up into their late teens.