As hard as it is to say. I did notice Ball got totally skinned when chasing a loose ball up front in a promising position not long after he came on. Workhorse yes but Pacey no. With the long haul to Perth and midnight kickoff perhaps suited better to younger legs.
I also think it has to do with a tactical choice of players to travel. Or he may have a family commitment and the team is away to Perth for a whole week, pretty much.