First: I have no idea what McVay's plan is..... 'my guess' is that he'll game plan this coming game not one iota differently than he would with Williams and Rivers both active.... but who knows?
So another guess... If anything regarding the running game is playing on McVay's mind I think it's the injuries..... and if, make that a big IF, he adjusts for that I think it will be in platooning this RB's. Limit each RB's exposure to injury. But again... I believe what is most likely, just one man's opinion, is that nothing changes.