Might disagree a little bit that it's not a "must win". I just base that on the stretch we have coming up where we play @Northwestern, Purdue, Michigan State, @Iowa, & Wisconsin. It's possible we could go 0-5 during that stretch so when you get games that are more winnable than others like Michigan, you have to capitalize on those.
It we can win our next 3 games @Michigan, Ohio State, and @Rutgers, that would put us at 6-1 before we head into that tough stretch. So that is why I think Michigan as well as Ohio State and Rutgers are "must win" games.