If the Big O goes we would be handicapped in the ruck. Maric can't ruck out a full season and Vickery is not physically ready to take the No 1 ruck duties through a game. Even if Vickery did, we have no one of his height and size to take the forward/ruck role unless you risk forcing McBean in early. Derickx is a lost cause.
Out of all of them, Tucky may be the one to go if any.