The Broncos' Defense Has Been Great, But Not Historically Great
There's no question that it's been entirely their defense that has carried the Denver Broncos to the Super Bowl this year.
We've all heard the old adage that defense wins championships, and it will never be proven more true than if the Broncos can pull out a win against the Panthers.
They have virtually no offense to speak of and have the top defense in the league, a unit that has managed to drag the corpse of Peyton Manning, Weekend at Bernie's style, to an AFC Championship.
While their defense is the class of the league, they haven't carved out a place in history for themselves, and without a Super Bowl win, they could quickly be forgotten in any discussion of top defenses of years' past.
One thing you can't take away from Denver is that they were by far the best defense in the league in 2015.
Our Net Expected Points (NEP) metric (which you can read more about here) measures how many points are added or subtracted compared to expectation level. When adjusted for strength of schedule, Denver dominated this metric, posting a Defensive NEP per play of -0.07 with the next best mark in the league being a -0.03 from Carolina.
They ranked fifth against the run with a -0.08 Adjusted Defensive Rushing NEP per play and first, by a wide margin, against the pass with a score of -0.10.
The distance between the Broncos and Panthers is part of makes what Denver is doing look special, but in reality, the gap is as much a reflection of their lack of competition for top defense than it is a reflection of their dominance.
Lack of Elite Defenses
As I mentioned, the Panthers ranked second in the league with a schedule-adjusted -0.03 Defensive NEP per play. While that's a solid number, this is the only time in the last decade that it would hold up as the second best in the league.
Over the last 10 years, their -0.03 would rank only as high as fourth (2014) and as low as ninth (2006 and 2007). On average, there would be 5.8 teams separating Carolina from the top defense in the league.
While this obviously doesn't say anything about the Broncos' performance, it does give us a bit of insight into why the Broncos may have felt like such an incredible defense when, as you'll see, the numbers say that they don't stack up as such over a larger sample in history.
How Denver Measures Up
We've covered how Denver performed this year, and we've looked at their competition for the top spot, but just where do they fall historically?
Our NEP numbers go back to 2000, and Denver's -0.07 Defensive NEP per play is only the 42nd best mark in our database. On average, 2.6 defenses per season finish with better numbers than Denver did this year.
Even if we narrow it to the last decade (the early 2000's boasted some impressive NEP numbers before substantial rule changes), they only come in at 16th. They also have the second-worst Adjusted Defensive NEP among league-leaders since 2000, with 2014 being the only other season that their -0.07 would be good enough for first.
They didn't pile up particularly impressive stats with takeaways and sacks either. They tied for seventh in the league with 27 takeaways and averaged one takeaway every 38.26 snaps, which ranked eighth.
Their pass rush is a huge story this week, after dismantling the Patriots' offensive line and throwing Tom Brady completely off his game. They were admittedly the best pass rush in the league this season, averaging a sack on every 12.24 opposing drop backs, but that's another stat that doesn't hold up well if we broaden the scope beyond 2015.
They only would have lead the league one other time since 2000 (in 2003), and on average, there have been three defenses per season with better sack numbers. The average drop backs-per-sack for league leaders has been 10.76, meaning Denver would've needed to record seven more sacks this season (58, compared to their 51) just to stack up as average among league-leaders.
I'm not trying to argue that the Denver defense isn't good. Their numbers are solid, and it's impressive how far they've carried a team that has absolutely no offense (Denver's offense ranks 28th in schedule-adjusted NEP per play).
If we look back at the last 10 or 15 years, though, there's nothing overly special about the unit, and without a Super Bowl win, they will be a quickly forgotten group.