Weather and refs. Unfortunately, I think those two factors will have the biggest impact on the game, low 30s with real feel in the 20s, 20-mph winds with gusts in the 30s. Game start is at 3pm, so it will get colder as the game goes on.
The Bears need to establish the run and stop the run. Whoever does that wins. Bears need a clean game from Caleb, no turnovers, take what the defense is giving you.