Name a QB that turned career around after bad start.
I am a big proponent of going with an unknown for a backup QB vs a backup QB that has a lot of experience, but the experience is that of being a bad QB.
Still, I understand many QBs are a product of the environment so I can see maybe taking a flier if that is a factor. Look at any QB under Jeff Fisher and you know that QB had one hand tied behind his back and that experience can be discounted somewhat as all QBs play under their capability for Fisher. See Nick Foles. Good QB before Fisher, horrific with Fisher, and good QB after Fisher.
But for the most part, I think going with the unknown is a better play if you are looking at finding a good one. The reality is if your starter is lost for the season, your odds go down like a rock. I get there have been some exceptions, but Kurt Warner won a superbowl as an unknown. In Foles case, he had played well prior to Fisher so I discount that one. I am talking about QBs that never played well, but went on and won later in their career as the light bulb came on.
The one that comes to my mind is Jim Plunkett, but I be curious if anybody can list some others.