The defense as a unit. They're the only reason this team has multiple wins at this point. They probably did enough to win the game without the offense taking the field (7-6 into garbage time, with Myricks TD).....and that's not an exaggeration. Think about that. It's astonishing to think that one team could win a B1G game if the bus carrying the offesne got lost and didn't show up to the stadium. That literally could have happened yesterday.
It's not as easy to hold down the Purdue offense (especially at home) as they made it look. They haven't scored fewer than three offesnive TDs or, fewer than 21 points this year (that's to Mich St. @ Sparty last week). Without the garbage time yards and TD, its extremely impressive.