This isn't an original thought (I think I owe IUTerry a hat tip), but it is worth noting: the Big Ten's various "tiers" are extremely well defined this year. Ohio State (14-1) and Wisconsin (12-3) are the top tier; Minnesota (3-12), Northwestern (2-12), and Penn State (1-13) are the bottom tier; and Illinois (9-6), IU (8-6), Iowa (8-6), Michigan State (8-7), Michigan (8-7), and Purdue (7-7) are the middle tier. What is so unusual isn't that there are obvious dividing points, but that the outcomes are almost entirely predictable by tier. Ohio State and Wisconsin went 1-1 against each other and 24-2 against the rest of the league. Wisconsin lost at IU and and at MSU. The bottom tier's results are nearly as uniform. Minnesota, Northwestern, and Penn State have combined for six wins. Purdue's loss at the Barn is the only win that the "little three" have claimed against any team but each other, at home or on the road. The muddled six have held serve against each other, winning at home and losing on the road, almost as a rule. Iowa won at Michigan, and that's it. As I type this post, Michigan is finishing a home win over MSU.
The point? IU has struggled on the road this year, but a loss tomorrow night in Evanston would be the worst loss by anyone in the Big Ten this season. Before a three game Evanston losing streak under Mike Davis, IU had not lost to Northwestern since 1988, home or away. Northwestern has never won in Assembly Hall and hasn't won in Bloomington since 1968, but even Welsh-Ryan Arena has been friendly to the Hoosiers. I'll add some more substance tomorrow. But this isn't so much a must-win as a can't-lose.