Let's say Nehe Milner-Skudder doesn't scrub up from his left calf injury and the All Blacks need to find a replacement for the World Cup final.
Simple, most would say. Do as in the semifinal victory and shift Ben Smith to the right wing and start with Beauden Barrett at fullback.
That change brought some extra zip to the backline and a try which tipped the gruelling contest back in the All Blacks' favour.
It might not be as simple as that.