1. Mullen himself has said that Russell is "not a package QB." We'll see him appear when we are up 3 touchdowns, or maybe down 3 touchdowns, but not in between. He also turns the ball over too much right now. That will change with experience, but right now it is what it is. Relf will have 4x the attempts of Russell this year just because he will have at least that much more playing time.
2. Relf will play because he challenges teams to put 8 men in the box. When that starts happening, we go five wide and Bumphis scores. When they readjust to that, Relf takes it in on the ground. He's not there to be a 60% passer, he's there to make sure the defense accounts for him, creating more one-on-one situations for the receivers and running backs. That's why this offense is successful. That's why it is a perfect fit for MSU. Your QB can be more of an athlete than a technician and be successful. You go to the line with a run and a pass play, there is a formula for calling the right one, and if you call a run, there is a formula for deciding if you keep it or not.
Like Coach said, all this hinges on Relf being able to be a serviceable passer. If he's not, we are screwed. If he is, we win a lot of games this year.
Russell will be a great QB at MSU, but he still has a lot to learn. I would rather him learn it in practice and against Alcorn State than against Auburn. Next year (or even late this year) the QB battle could get very interesting.