If Carr plays bad (which I doubt he will) and all reports are that either Rattler or Haener have been performing well I think this franchise and ownership will be ready for the new leader under center, I do not think Rattler or Haener were drafted to hold clip boards but with an eye for the future.
The way this offense is designed and we have seen work in previous stops the QB position is prime for a game manager which I think both Haener and Rattler can do with the exception of Rattler being a natural talent as a passer but Carr too can thrive in an offense that is heavy run base with play action passing.