Do Top Defenses Regress? A Historical Study

Dennis Wierzbicki-USA TODAY Sports

"The Bears defense is going to regress." That refrain has been so common among national writers that it's become received wisdom. Bears fans, understandably, have been touchy about the subject.

It's easy to understand the reasoning. In the salary cap era, sustaining a top-flight unit is harder than ever. Analysts have shown that turnover rates tend to vary wildly from year-to-year. Fumble recoveries are highly dependent on luck. Bears fans, on the other hand, argue that the unit simply has too many top-tier players in their prime to meaningfully regress, even with a DC switch.

Rather than reheat the same arguments over and over, I decided to take a look at the historical data. What happened to the NFL's top defenses the next season? Did they actually regress? If they did, was it a product of dumb luck or were there other reasons at play? If they didn't, what was different about those teams?

I used Football Outsider's DVOA for team defense, and limited the study to the last 10 seasons (going back to 2008).

2008 - Pittsburgh Steelers. 12-4, Super Bowl Win. Pass Rank: 1. Rush Rank: 2. Turnovers: 37

Next Season Ranking: 9th. 9-7, missed playoffs. Pass Rank: 14. Rush Rank: 8. Turnovers: 22

Notable Offseason Losses: FS Antony Smith. CB Bryant McFadden.

The 2008 Steelers had a DPOY performance from James Harrison (16 sacks), another double digit sacker in Lamarr Woodley, veteran ILB James Farrior patrolling the middle, and suis generis SS Troy Polamalu as their wildcard. They lost a couple starters in free agency, but no one major. But Farrior and Harrison were on the wrong side of 30 (34 and 31, respectively). More importantly, Polamalu got hurt in their first game of the season -- the irreplaceable safety only played 5 games. Between injuries and in performance, the Steelers fell from top-tier to above-average, and they missed the playoffs.

The Takeaway: It's tempting to see this as the crest of a "success cycle." As we'll see later, this was not quite the case. Polamalu really was the engine that made that defense run, and his injury proved too much to overcome.

2009 - New York Jets. 9-7, lost AFC Championship to Colts. Pass Rank: 1. Rush Rank: 7. Turnovers: 31

Next Season Ranking: 5th, lost AFC Championship to Steelers. Pass Rank: 7. Rush Rank: 2. Turnovers: 30

Notable Offseason Losses: CB Donald Strickland, FS Kerry Rhodes.

Despite adding CB Antonio Cromartie through a trade, the vaunted Jets pass defense took a step backwards. But the team actually won two more games. The offense moved from below average to middle-of-the-pack, and the team actually got slightly more turnovers. That was enough to keep them afloat.

The Takeaway: Everyone remembers those Rex Ryan defenses as impenetrable against the pass, but this wasn't the case in Year 2. But I doubt even Jets fans remember this. If the offense can step up even a little bit, it can counteract regression elsewhere.

2010 - Pittsburgh Steelers. 12-4, Super Bowl loss to Packers. Pass Rank: 3. Rush Rank: 1. Turnovers: 35

Next Season Ranking: 7th. 12-4, lost Wild Card to Broncos. Pass Rank 3. Rush Rank: 15. Turnovers: 15

Notable Offseason Losses: None that I could see

After a downyear, the Steelers defense bounced back. Harrison and Farrier, if not quite at their peaks, still proved to be ageless wonders. The 2011 Defense looked largely the same, and indeed in superficial numbers their defense still looked top tier (they lead the league in points and yards allowed). But below the surface level, their rushing defense took a step back.

The Takeaway: Let's see: the pass rank stayed the same, but the turnovers absolutely plummeted. The rush defense moved back to middle of the pack. But the record remained the same. Makes perfect sense! Maybe sometimes regression doesn't matter! Or taking a slightly longer view, the Steelers had a top defense for 4-5 seasons, near the top when everything broke right, and still in the top 10 when things didn't.

2011 - Baltimore Ravens. 12-4, lost AFC Championship to Patriots. Pass Rank: 1. Rush Rank: 7. Turnovers: 26

Next Season Ranking: 19. 10-6, won Super Bowl. Pass Rank: 13. Rush Rank: 25. Turnovers: 25

Notable Offseason Losses: DC Chuck Pagano. Do Jarret Johnson or Cory Redding count?

Team builders talk about success cycles, and this was clearly the last hurrah of the Lewis/Suggs/Reed/Ngata defense. Chuck Pagano left to coach the Colts, and was replaced by Dean Pees. Both Lewis and Suggs missed significant time, and even mainstays Ngata and Bernard Pollard missed a couple games. The cumulative effect lead to a pretty steep dropoff.

And yet... they won the Super Bowl! A midseason OC change to Jim Caldwell helped revitalize Flacco, new kicker Justin Tucker turned out to be money, Hall of Famer Champ Bailey blew his coverage, and the rest is history.

The Takeaway: Age and a DC switch did a number on this defense. But the real lesson is to find a way to get into the playoffs.

2012 - Chicago Bears. 10-6, third in NFC North, missed playoffs. Pass Rank: 1. Rush Rank 1. Turnovers: 44(!)

Next Season Ranking: 25th. 8-8, missed playoffs. Pass Rank: 17. Rush Rank: 32. Turnovers: 28

Notable Offseason Losses: HC Lovie Smith, Brian Urlacher, Nick Roach, D.J. Moore

Lovie Smith got canned, Urlacher retired, Henry Melton got hurt and... you know what, I don't really feel like talking about this, OK?

The Takeaway: Looking back, it's easy to see that Emory completely misread the situation. 2012 was the last hurrah of the great Lovie defenses, fueled by an absolutely insane turnover rate. Almost all the stars on the D were on the wrong side of 30, and very much "Lovie guys." It's temping to see parallels between this team and the current one. But the current defense is significantly younger, and our defensive coordinator left under much better circumstances.

2013 - Seattle Seahawks. 13-3, won Super Bowl. Pass Rank: 1. Rush Rank: 7. Turnovers: 39

Next Season Ranking: 1st. 12-4, lost Super Bowl to Patriots. Pass Rank: 3, Rush Rank: 2. Turnovers: 24

Notable Offseason Losses: CB Brandon Browner

Next Season Ranking: 4th. 10-6, lost Divisional Round to Panthers. Pass Rank: 3. Rush Rank: 3. Turnovers: 23

Notable Offseason Losses: DC Dan Quinn, CB Byron Maxwell, LB Malcolm Smith

Our first repeat! The Legion of Doom is the best-case scenario of our team: a young, swaggering defense built through the draft and shrewd trades.

The Takeaway: Even after DC changes and losing players to free agency, the Seahawks were still the #4 ranked defense. They were a top 5 unit from 2012 - 2016. Attrition, age, and egos eventually took their toll. But would any Bears fans complain if we fielded a top 5 unit for five straight seasons like they did?

2015 - Denver Broncos. 12-4. won Super Bowl. Pass Rank: 1. Rush Rank: 4. Turnovers: 27

Next Season Ranking: 1st. 9-7, missed playoffs. Pass Rank: 1. Rush Rank: 21. Turnovers: 27

Next Season Ranking: 10th. 5-11, missed playoffs. Pass Rank: 15. Rush Rank: 3. Turnovers: 17

Notable Losses: DE DeMarcus Ware, DE Malik Jackson, LB Danny Trevathan, DC Wade Phillips

Another repeat! The 2015 Broncos were built with a mix of good draft picks (Von Miller, Danny Trevathan, Malik Jackson, Chris Harris) and acquisitions (DeMarcus Ware, Aqib Talib). Wade Phillips worked his usual magic. I think they're actually a good comparison with the 18-19 Bears: the CBs were not traditional shutdown guys, but they were all ballhawks. An imposing front-7 forced QBs to rush throws, making mistakes the secondary could capitalize on.

The next season they were still good enough to be in 1st. But with Peyton Manning's retirement, they began a QB carousel that continues to this day. Attrition slowly drained the talent (Trevathan to the Bears, Jackson to the Jaguars, Ware to retirement), and Phillips left when the staff turned over.

The Takeaway: Stopping organizational and QB churn is essential to not wasting a great defense.

2017 - Jacksonville Jaguars. 10-6, lost AFC Championship to Patriots. Pass Rank: 1. Rush Rank: 27. Turnovers: 33.

Next Season Ranking: 6th. 5-11, missed playoffs. Pass Rank: 6. Rush Rank: 7. Turnovers: 17.

Notable Losses: CB Aaron Colvin, LB Paul Posluszny

This is the nightmare situation for Bears fans. The 2017 Jaguars were a No-Fly Zone, impenetrable against the pass (surprisingly bad against the rush). The 2018 Jaguars actually got better against the rush, but the dropoff in pass defense was enough to drop their defense just outside the top-5. The offense, on the other hand, went from a middle-of-the-road unit spearheaded by Leonard Fournette's rushing, to a dumpster fire in 2018.

The Takeaway: When experts say that the Bears defense will regress and they'll miss the playoffs, this is almost certainly the case study they have in mind. But there's some key differences.

After giving Bortles a massive extension, the offense absolutely collapsed. It's possible that Trubisky also takes a huge step back. But it's worth noting that Bortles was playing his 4th season in 2017. Trubisky may have been average in 2018, but Bortles still never managed to have a season anywhere as good as that. The Jaguars were counting on Fournette, and when he got hurt and/or disgruntled, the toxicity spilled out into the rest of the organization. Jalen Ramsey alone accounted for a huge chunk of that pass defense, and a slight down year meant the secondary had less margin for error.

2018 - Chicago Bears. 12-4, lost NFC Wildcard to Eagles. Pass Rank: 1. Rush Rank: 2. Turnovers: 36

Next Season Ranking: TBD

Notable Losses: CB Bryce Callahan, SS Adrian Amos

And so we finally come to the Bears. What are some of the patterns we notice looking back at all this?

- Our turnovers were high in 2018, but not astronomically so, and in line with other top defenses from this era.

- Our defense isn't filled with guys on the wrong side of 30 (even Akiem Hicks is only 29). We are not at the crest of a success cycle.

- Injuries to key guys can derail a season. We have no replacement for Mack. Much of that is just a function of luck, and it certainly doesn't take an enormous brain genius to realize that losing Mack would hurt the Bears.

- There's only one instance I could find of a DC change while still remaining a top defense: the 2012 Seahawks (second only to the Bears) going from Gus Bradley to Dan Quinn. Even so, they were very much running Pete Carroll's system. But then again, I cannot find another instance where a team lost a DC and replaced him with another guy who ran a top defense, as we did with Pagano.

The Takeaway: We have examples of two defenses that stayed on top, and we have a lot of similarities with both of them: lots of homegrown talent, supplemented by shrewd trades and FA signings, almost all under 30.

As a fan, I am certainly biased. But it's just as lazy to assume that a top defense must regress. We have two counterexamples in the last 5 years!

Worst case scenario, we have some back injury luck, but we probably still remain a top 5-10 unit. Best case scenario, we remain a top 5 unit for the next 3-4 seasons.

The defense looks poised to hold up their end of the bargain. Now it's up to Nagy and (especially) Trubisky.

This Fanpost was written by a Windy City Gridiron member and does not necessarily reflect the ideas or opinions of its staff or community.

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