Well, in my opinion this award should go to the coach who's team exceeded expectations by the biggest margin. Everyone knew the Pats were going to be legitimate contenders this year, though nobody thought they'd go 16-0. Belichick did a fantastic job keeping his team focused all year and as usual he made tremendous adjustments in the face of adversity. Certainly anyone with an IQ in the double digits could make a case for him.
However, I think this award should've gone to MaCarthy in Green Bay. They weren't expected to do anything at all this year and look at the season they've had. Again, to me, it's all about exceeding expectations, and nobody did a better job of that this year than MaCarthy did.
Just my 2 cents, take it for what it's worth.