If you mean at the highest levels of sport though, great genetics will completely overwhelm whatever work the less genetically gifted are doing.

This to me is the real problem with over specialization. You have less than gifted parents living out their athletic dreams through their kids but if the parent wasn't that good at the sport there will be correlation with the kid not being that good.

Kids shouldn't specialize in sports too young because there is such a great chance they are not in the right sport at 11.