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Predicting defensive regression; four factors that could affect the Buffalo Bills

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Should the Bills expect any in 2020?

Defensive success year over year has proven difficult in the NFL as of late. Elite defenses one year might be average defenses the next, and fantasy football players lulled into expectations of continuation fall prey to the concept of defensive regression in the middle rounds of their fantasy drafts every year. Some defenses simply don’t stand up to the test of time, but why? Is there some method of ascertaining whether a defense might be at risk for a regression?

Look over the internet for those who are bearish on the Buffalo Bills in 2020 and you may see comparisons to the 2017 Jacksonville Jaguars and the 2018 Chicago Bears. Both teams had young quarterbacks who were expected to take the next step the year after their elite defenses carried them to the playoffs, and both of them disappointed the year after. While there are clear similarities in the situations with those teams and the 2019 Buffalo Bills, I believe that the answer to four specific questions, when specifically used in reference to the 2017 Jaguars and the 2018 Bears, can help an observer not be completely in the dark as to whether or not the defenses that carried a team the previous year will continue to be able to do so the next year...


  1. Was the adjusted sack rate unsustainable?

Adjusted sack rate (see footballoutsiders.com) measures what percentage of a pass play ends in a defensive sack (or a intentional grounding penalty which has the same negative impact on the offense) adjusting for down, distance, and opponent. The NFL average for this statistic typically ranges between 6.0% and 7.5%. In 2017, the Jacksonville Jaguars had a staggering 9.1% adjusted sack rate. This level of sack production is almost impossible to sustain given that pressures in and of themselves have shown to have variance (the Jaguars had a 39.1% pressure rate that year per PFF, 3rd in the NFL), and the pressure to sack ratio itself has shown that it will often normalize at levels far beneath the threshold that the Jaguars set in 2017.

2. Was the defensive production due in large part to turnovers and/or defensive touchdowns?

The 2018 Chicago Bears led the league in turnovers forced (36), interceptions (27), and interceptions returned for touchdowns (5). Scoring five touchdowns on interception returns in a single season is a staggering statistic and one that is high unlikely to be replicated the following year. Forcing turnovers is not an entirely random statistic, but forcing them at that level is unsustainable. In the inverse, the 2018 San Francisco 49ers forced the fewest turnovers of any team in league history, and after some additions to the defense in the offseason, the 2019 49ers saw the progression to the mean with their defense that helped lead them to a Super Bowl appearance.

3. Did the team lose significant defensive personnel or coaching?

There were many pieces written about how the Chicago Bears wouldn’t miss Vic Fangio in 2019 and that new defensive coordinator Chuck Pagano would keep the unit at an elite level. The Bears defense in 2019 was a good defense, ranking fourth in points allowed and eighth in yards allowed, but the drop off to 22nd in turnovers forced didn’t allow them to carry the team the way they had in 2018.

4. Did the team face a markedly below average slate of quarterbacks last year?

The 2017 Jacksonville Jaguars faced the following quarterbacks during the regular season:

  • The combo of Tom Savage and rookie Deshaun Watson
  • Marcus Mariota
  • The combo of Ryan Mallett and Joe Flacco
  • Josh McCown
  • Ben Roethlisberger
  • Jared Goff
  • Jacoby Brissett
  • Andy Dalton
  • Phillip Rivers
  • DeShone Kizer
  • Blaine Gabbert
  • Russell Wilson
  • Jimmy Garoppolo

The 2018 Jaguars faced:

  • Eli Manning
  • Tom Brady
  • Marcus Mariota
  • Sam Darnold
  • Patrick Mahomes
  • Dak Prescott
  • Deshaun Watson
  • Carson Wentz
  • Andrew Luck
  • Ben Roethlisberger
  • Josh Allen
  • Josh Johnson
  • Ryan Tannehill

Simply swapping Brissett twice for Andrew Luck twice (the Jaguars are divisional opponents to the Indianapolis Colts) would be enough to notable tip the scales in the favor of 2018 when it comes to average quarterback strength and when it’s combined with the other patterns indicating potential regression outlined above, the Jaguars defense predictably took a step backwards.

But where will the Bills’ defense land? Let’s outline four questions as they relate to the 2020 Buffalo defense versus 2019:

  1. Was the adjusted sack rate unsustainable?

Buffalo’s adjusted sack rate was 13th in the league in 2019 at 7.2%, barely nudging out the 7.0% NFL average last year. It is not notable in its lack of sustainability.

2. Was the defensive production due in large part to turnovers and/or defensive touchdowns?

The 2019 version of the Bills’ defense ranked 10th in the league in turnovers forced. They did not score a defensive touchdown.

3. Did the team lose significant defensive personnel or coaching?

The Bills saw starters Jordan Phillips and Shaq Lawson leave in free agency and replaced them with Mario Addison, Vernon Butler, and Quinton Jefferson. They lost defensive line coach Bill Teerlinck and replaced him with Eric Washington.

It is the opinion of this writer that those moves constitute an upgrade overall for the Bills defense.

4. Did the team face a markedly below average slate of quarterbacks last year?

In 2019, the Buffalo Bills faced the following quarterbacks:

  • Sam Darnold
  • Eli Manning
  • Andy Dalton
  • Tom Brady
  • Marcus Mariota
  • Ryan Fitzpatrick
  • Carson Wentz
  • Dwayne Haskins
  • Baker Mayfield
  • Brandon Allen
  • Dak Prescott
  • Lamar Jackson
  • Duck Hodgins

In 2020, the Bills are scheduled to face the following quarterbacks:

  • Sam Darnold
  • Ryan Fitzpatrick
  • Jared Goff
  • Derek Carr
  • Ryan Tannehill
  • Patrick Mahomes
  • Jarrett Stidham
  • Russell Wilson
  • Kyler Murray
  • Tyrod Taylor
  • Jimmy Garoppolo
  • Ben Roethlisberger
  • Drew Lock

Based on that current slate, it is the opinion of this writer that the 2020 quarterbacks the Bills are scheduled to face pose a more serious threat than the 2019 group did.

Based on the answers to the questions above, it appears unlikely that the Bills will experience regression to the same level seen from the 2017 Jaguars and the 2018 Chicago Bears. Although the quarterbacks the Bills are scheduled to face are more formidable than those they saw in 2019, that by itself would not appear to be significant enough to cause the type of drop necessary to invalidate the defense being a meaningful contributor to a potential playoff team.


...and that’s the way the cookie crumbles. I’m Bruce Nolan for Buffalo Rumblings. You can find me on Twitter @BruceExclusive and look for episodes of “The Bruce Exclusive” every Thursday and Friday on the Buffalo Rumblings podcast network!