Preview: Steelers at 49ers, December 19 2011

For this week's preview, I am compelled to make a generic "keys to the game" list, but statistically informed. However, I can't call them "keys" because everyone else does that. So, in honor of the 49ers, I'm calling them "gold nuggets", and there are 49 of them! Just kidding, I wouldn't do that to you, but the square root of 49 is 7, making that the perfect number of gold nuggets for this preview.1. Make it a defensive battle.The Steelers are current ranked fifth in offensive DVOA and ninth in defensive DVOA, while the 49ers are ranked 21st offensively and third defensively. As there is obviously a question of how well the Steelers offense will perform with Ben Roethlisberger's injury, the defense will have to steal the show in this game, because I don't see the offense scoring more than 20. I'd be glad to be wrong, though.2. Involve Mendenhall in the passing game.To protect Ben (or Batch), there will be plenty of short pass...