lando - first of all - take a chill pill dude - it's just some friendly ribbing!

Secondly, the two lots of athletes are trained in different ways. Don't be so naive as to think your sport's athletes are superior to another. AFL/NFL players are trained for short burst of power with little need for endurance while Rugby players are trained for less power and more endurance. AFL/NFL players are also far more specialised where as Rugby players are more generalist in their skill sets. Put a running back into a Rugby game and he would blitz most of the current international Rugby players when it came to speed on the field, but he wouldn't last a full 80 minutes of play. He also wouldn't be much good on defence as he has not trained for it. Put a line backer in a Rugby game and he would be great at some of the set pieces but he would be too bulky, and therefore slow, to be of much use on attack or defence and again would not last the full 80 minutes (I reckon he would struggle with 20).

By the same token, put a rugby player into an AFL/NFL game and they would struggle to match the intensity of the other players. These are generalizations of course, and I am sure there are players that could cross over between the two games.