Frankly, if most teams in the NFL lose their starting QB for a significant amount of time, they're screwed. The fantasy is that one has a future Tony Romo or a Nick Foles that can carry a stacked team. The reality is that you might get roughly 3~5 games out of your backup before it all falls apart. Remember all of Peyton Manning's backups? Utterly terrible.
Speaking of backup QB's, Raiders may need one.
https://www.nfl.com/news/raiders-qb-aidan-o-connell-suffered-fractured-wrist-in-preseason-finale-expected-to-be-out-6-8-weeks