As
@is the answer jesus noted, I'm also more concerned about backup QB than I am about #2 RB. There are many UDFA options at RB, players shake loose in camp, etc.
Another QB is essential, Bills will get one for the PS. I don't want to be in the position of an Allen injury for >2 games and having to pluck someone off another team's PS, or a semi-retired QB playing Madden on the couch, in order to have a chance at winning. The East will be a lot tighter this year top to bottom, Bills have a tougher schedule, and 1-2 games decided by injuries, health, and backups playing up to starter level could be the difference for the eventual division winner.