During the 2015 regular season, the Broncos and Panthers allowed the NFL's fewest and second-fewest yards per play, respectively, and finished 1-2 defensively in Football Outsiders' defense-adjusted value over average (DVOA) ratings. It's only the eighth time the top two DVOA defenses1 have met in a Super Bowl, and the average defensive index of the teams involved ranks third all-time, trailing only Super Bowls XIV and IV. Everyone is obsessing over the study in contrasts at quarterback - Cam Newton vs. Peyton Manning - but it's the two defenses that should be taking center stage in the lead-up to Sunday, because by just about any measure, this is one of the best defensive matchups in Super Bowl history.