Ziebell would be my choice. Obviously in an ideal world we have more then 3 key defenders on the list.Has Scott played as a 3rd tall defender? It's rhetorical. Walker isn't playing, Bonar unavailable. Who would you select to play as a 3rd tall down there?
I understand your rationale, but I’m also not sure whether Young will play that role.
It is highly likely that one (or even both) of Young & Scott will spend a fair bit of time on a wing on Sunday. I think Powell should be playing ahead of whoever is going to be playing on a wing.