If the defense continues to play like they have. BYU will likely be in every game this year. What will turn games are turnovers. BYU was lucky that those three turnovers didn't cost them the game. Retzlaff was responsible for all three and two were completely inexcusable and the third was kind of a fluke but a throw he probably shouldn't have made.
My point is that this year's team needs a game manager at QB. Considering how careless Retzlaff is with the ball (he had a fumble vs. SIU but it was recovered by BYU) is highly doubtful he can fill that role.
The question is whether or not Bohannon would fill that role better. My guess is that due to his experience, that he would. And I do believe one way or another he will get the chance you show it.