Well, it's got to be multiple defensive players.
Starting with the defensive backfield, a couple of interceptions would be a huge help. Their QBs aren't great passers but they've only thrown 2 interceptions in 3 games and they were both against Temple. Linebackers and D-line need to stuff the run. They're averaging 5.5 yards per rush. Even in the blowout loss to Temple they averaged 4.3 per rush.
Their defense is allowing only 2.8 yards per rush although that's a bit skewed because of the .5 yards per rush allowed against Bowling Green. Still, I don't think we're likely to get 200 rushing yards against them so the QB protection, the QB, and receivers all have to be sharp. They're defense gave up 260+ yards passing to both Texas and Temple so pass defense isn't the strongest part of their game. Bowling Green managed to get 143.