Slade covers
Slade covers 10. So if Marcus goes off Fin stays put and (hopefully) Steward comes in at 15. If both Smiths are nobbled then Slade moves into 10, and it may be the plan to have Daly on the bench who covers 15, centre and wing, so he comes in at centre with Steward at 15.
All this being said I still wonder whether these rumours are BS. Could SB have learnt from last weeks tactical error of releasing the team sheet too early, and be playing a cheeky smoke screen blinder to throw off the French? Doubt it, but heres hoping...