WP,
I know you've picked up on teh lack of most youngsters defensive side to their games.
Its all education. No-one picks up a footy at the age of 10 and wants to play AFL by minding another players backside. Everyone wants the ball and to be involved. Post and many others wil learn that their role in the side is to not only get your hands on the footy and keep possession but stop the opposistion getting it at all costs and get it back off them when they have it.
It's just footy education. 2nd year he's a baby, needs to be taught the right lessons.