From your answer, I am guessing you didn't see the Iowa State game. If I hadn't seen both games and was judging off of the scores, my view on next weekend's game wouldn't have changed much either.
First, let's assume that UNI and Illinois State are both good BCS teams, however, Illinois State is the higher ranked team. Iowa dominated Illinois State on the field and on the scoreboard. ISU dominated Northern Iowa on the scoreboard, but the game on the field was a bit unusual.
The ISU-Northern Iowa score looked like it did because UNI continually shot itself in the foot in the battle for field position. Because of UNI's inability to cover punts and two costly turnovers, Iowa State started 6 drives in the 2nd and 3th quarters at its 49 or better. And, 3 of those drives started no farther away from the goal line than UNIs 26 yard line. And yet, the ISU offense (remember one score was a punt return) could put no more than 24 points on the board against UNI.
UNI played this game with a first-time starter who was replaced late in the 3rd quarter for being ineffective. UNI seemingly had 3 and out after 3 and out during the first three quarters, then their punter would come in and kick a low line drive punt to Allan Lazard who was able to repeatedly catch the ball with no UNI player within 15 yards of him (seriously, I am not exaggerating).
ISU returned 8 punts, averaging 24.1 yards per return. That is 8 punts with a net punting average on those 8 punts of under 20 yards. That is barely different than if UNI had thrown 8 interceptions. Add that to the two costly turnovers that UNI actually had, and it is like ISU was the beneficiary of 10 UNI turnovers, yet the ISU offense could only put 24 points on the board.
ISU's defense might be average. It is hard to tell because UNI's offense was so bad. On offense, ISU's receivers are above average, their quarterback is average, and their line is below average, and their running backs are awful. The place where a Big 5 school is suppose to impose its will against a BCS defense is with the line play and rushing attack. ISU only gained 77 yards rushing on 2.4 yards per carry. If you take away one long run, they gained 44 yards on 1.3 yard per carry against UNI.
ISU is not going to beat Iowa on the ground. They have a passing game that is probably above average, but Iowa's strength on defense is probably against the passing game. As long as Iowa either punts away from Allan Lazard or is decent in punt coverage, I feel much better about Iowa's chances against ISU than I did 48 hours ago. Much better.