"An NFL player found that he managed to be good at rugby after 2 months of practice, but when he tried to do gymnastics (or cycling or tennis or motorsports or

"An NFL player found that he managed to be good at rugby after 2 months of practice, but when he tried to do gymnastics (or cycling or tennis or motorsports or ...) in the same time frame, the results were terrible." What does that tell you the sports he tried to do? Not much. It's all about his previous experience and skills.