In my opinion, I would have to say it's either the Packers or the Steelers.
The Steelers are a contender because of Troy Polamalu and the Packers are great because of Clay Mathews.
Since week 1, the Packers have been doing great, not just because of Clay Mathews but because of how well their whole team has been playing. Just because they lost to Washington, a game that they should have won, doesn't mean that their defense is bad. It means that they're not playing as a team. Aaron Rodgers missed a few open receivers and the receivers missed a couple good passes. Overall, their defense is great and they're going to make the playoffs.
Now let's talk about the Steelers. Don't even get me started on the Steelers. I thought they'd be terrible because of Ben Rothlesburger's suspension and because I thought their back up QB's were terrible. During week 1, they blew me away. In weeks 2 & 3 their defense was amazing, especially Polamalu. When they lost to Baltimore, I was pretty surprised but they didn't lose by that much.
Well that's all for this week NFL RUSHERS.
Don't forget...Bills Rock!