The problem i can see is that normally they will take the starting hooker off and put him on for the final stages of the game. If that happens than Gidley goes back to fullback, who goes off? Do they take off a fairly fresh Morris or take off another outside back. Maybe they're worried Lyon wont make the 80 mins.
They`re probably more worried that Barret won`t make the 80 minutes. If that`s the case, then Gidley to five-eight, Hayne or Morris fullback, etc. OR: Lyon to five-eight, Hayne or Morris to centre. There`s a lot of permutations because Lyon can play centre or five-eight; Barret can play five-eight or lock; Hayne - fullback, centre, wing, maybe five-eight?; Gidley fullback, five-eight, hooker / half; Morris centre or wing or fullback. Our whole backline are utility players.