No, I don't think it is unreasonable to expect an Australian player to play well for 80 minutes.Is it really unreasonable to expect an Australian rugby player to play 80mins if needed? Whitelock and Retallick are both 80mins players.
Props are one area, due to the power nature of the game which stand to benefit by keeping their match time to the 50min mark.
But certainly for locks and backrowers, the relationship between impact and match time isn't inverse.
Do you disagree with the premise that some players have a greater ability to provide impact over a shorter period of time than others?
Of those two great ABs locks I would say Retallick is a more explosive player and would be able to provide more impact in half an hour than Whitelock.
I think the bench role is pretty different to starting and some players are better suited it at than others.
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