I think you can make the argument that the defensive performance against Wisconsin was the best of this season. You can surely argue for the Iowa game, but outside of two drives the Badgers were kept silent on offense. During the last two home games, the defense has allowed just one touchdown (not counting the fake field goal touchdown by Iowa).
Overall against Iowa and Wisconsin, the defense has allowed 17 points and 619 yards over the course of 145 plays. That’s an average of 4.2 yards-per-play which is .6 less than its season average of 4.8 yards.