Rush needs to be the backup .. it's that simple. It's not hyperbolic at all nor is it a byproduct of how pathetic Moore has looked. Rush is exactly what you want if you don't have a proven solid veteran backup and that's a guy that has the potential to be a starter one day. I'm not talking about him supplanting Dak by any means, but if Dak is lost for several games or the season, you don't want a bandaid .. you want a guy who can come in, continue to get better and win games for you.
Moore has peaked .. he peaked in Detroit. Moore has already reached his potential. Whether Rush is a future starter for some team or a Matt (not Kellen) Moore backup type, he at least right now has potential to improve and help you win games, neither of which Moore has or provides.