Good call SeaTown. You don't need a starter in waiting, you just need a Gary Kubiak that can come in and play the same offense you're playing. In fact, those situations are better. I remember when the Raiders had three guys that were all starter level and it just created chaos. Once they jettisoned Marc Wilson and turned everything over to Plunkett and said "he's the guy" they won a lot more. Having those two jostling for starts from week to week was bad for the team.
You need a Doug Williams. A guy who can play hard, rally the team, is liked by teammates, and can throw the ball. You don't need Jonny Unitas on the sidelines. Doug stepped in and won a Superbowl just by being a super well prepared guy, which he always was, even in his bad days with the Bucs, nobody ever questioned Doug's preparation. Jeff Hostetler comes to mind too. He was given a chance as a full time starter in Oakland and just didn't have it, but as a part timer he was spectacular. He was a great backup, was a team oriented guy, and when he came in everybody stepped up a bit and helped him succeed because they knew they had to.