Nick Foles, Earl Morall, Jeff Hostetler and I am sure others helped lead teams to and through playoffs. I think the Bills make the playoffs even if Josh misses a small number of games, regardless of who the backup is. I don't think the Bills make a run through the playoffs without Josh. Clearly if the decision was "win the super bowl, or get a first" everyone would pick "win the super bowl". Its not at all obvious those are the two choices.