I'm not sure if it's ever happened before, but Iowa is likely to be undefeated heading into their final regular season game. They have been playing well this year, and when you look at their schedule, they have perhaps the easiest schedule of any team in the league. They don't play OSU, MSU, Michigan, or PSU. Their toughest remaining game before coming to Lincoln looks to be at Indiana.
With so many teams playing each other, they would easily be in the top 5 when they arrive assuming they are undefeated.