Post wont get a game because he was shocking in round one, and is being made to earn his position by being more agressive at the contest and the man.
Vickery gets a game because he can play ruck and give maric a chop out. Also because he finished 5th in the best and fairest and is a 200cm forward ruckman. You dont lose abilitity but you can lose form, absolute key to the tigers future that he turns it around, and will be given every opportunity.
Griffiths gets a game because he is a 200cm key back, who can also play forward in20 years old, is super quick and can kick the ball 70 metres. With Grimes out, Griffiths is a much better chance of stopping Roughead and the resting Hale than Post, who was absolutelu killed in round 1 against the Hampson ( some people have very short memories )
I don't think people understand how crucial that big, key back position is to fill. If Griff can hold down that position, it means that we don't need to target a KB in free agency, and we can focus on our other needs, midfield depth, and a Ryan O'Keefe type.
Miller has been dropped because Vickery may play in a tiger premiership, but Miller definatly wont.
Both decisions are completely rational and logical