I think that McMullen is--for the lack of a better term--"winning over" Tressel with his play. Look at what he's done since last year. He's never had a bad game (again, since last year...this doesn't include the 2001 Illinois fiasco). Last year he was 25-31-0 (80.6%) for 315 yards and 2 TDs. This year he's 43-62-2 (69.4%) for 507 yards and 5 TDs. That makes him 68-93-2 (73.1%) for 822 yards and 7 TDs over the last two seasons. He's averaged just under 9 yards per attempt, which if I recall correctly is a damn good average. His 7/2 TD/INT ratio ain't bad either.
The offense has looked good whenever he's been in there, and I think Tressel would like to "ween" him into the offense over the last few games of the year, as to not be "disloyal" to Krenzel.
Krenzel, when he's on, is an outstanding overall QB. When he's on his normal accuracy (around 60%), he's an excellent QB, But when he's off (ala SDSU and most of the Wisconsin game), our offense just dies. Craig has superb confidence, but when does finally get rattled, he never seems to regain composure. Last year, I never really saw him rattled, but since he threw that pick on the first play of the SDSU game, he seems vulnerable to getting rattled by a couple bad plays.
If there were some way we could keep Krenzel at his top confidence, then I'd start him in a heartbeat and keep him in. But as soon as I see a hint of him being rattled, in goes McMullen. That's how I'd do it...and maybe Tressel could be thinking along the same lines.