There's an old cliché in football: "Offense wins games, defense wins championships."

And true to form, a number of teams fielding elite defenses during the early part of this season look like they could be legitimate Super Bowl contenders.

Here at numberFire we have our signature metric known as Net Expected Points, or NEP. What this measures is a given play's contributions to a team's chances of scoring above or below expectation. In the case of defenses, if a unit makes a play that decreases the opposing offense's chances of scoring below expectation, they receive credit for that in the form of a negative score proportional to the magnitude of that given play.

With all that being said, which teams according to our metrics have fielded top-tier defenses that look like they could help propel their teams to a trip to Santa Clara in February?