Let's talk defensive styles

I just spent a little time with a couple sources for 2017 team stats (PFF and Football Outsiders) that gave me some team tendencies. We tend to categorize defenses fairly crudely, either solely by base defense formation, by generic terms like 'one-gap 3-4' vs 'two-gap 3-4' or something, or by coaching tree. There's some truth in these, but I wanted to go deeper. I just created a spreadsheet (you can click that link to see) that has percentage and rank for:

Four Pass-Rushers
5+ Pass Rushers (Blitzes)
2-3 Pass Rushers
Defensive Back Blitzes
Man coverage
Zone coverage

In other words, a blitz in a 3-4 would mean 2 stand up rushers, not just 1. This makes the comparison apples to apples. It was interesting to see that 3-4 defenses still frequently sent 5 guys, far more often than most 4-3 teams.

The man vs zone determination was as follows:
"Broadly, Cover-0, Cover-1 and Cover-2-man are considered man-coverage schemes, while Cover-2, Cover-3, Cover-4 and Cover-6 are more zone schemes. "

Using these stats, I grouped defenses. Here are the categories that I found:

3-4 High to Moderate Blitz, High DB Blitz, High to Moderate Man

• Cardinals, Ravens, Jets, Titans, Texans, Packers

3-4 High Blitz, Low DB Blitz, High Man

• Broncos, Rams

3-4 High Blitz, High DB Blitz, High Zone

• Steelers

3-4 High Blitz, Low DB Blitz, High Zone

• Redskins

3-4 Moderate Blitz, High Max Coverage, Low DB Blitz, Moderate Man/Zone

• Bears

3-4 Low Blitz, Low DB Blitz, High Man, High Max Coverage

• Patriots, Chiefs, Colts

4-3 Low Blitz, High Man

• Seahawks, Falcons

4-3 Low Blitz, Moderate Zone

• Jaguars, Eagles, Bengals

4-3 Moderate/Low Blitz, Moderate Zone

• Vikings, Bills

4-3 Low Blitz, High Zone

• 49ers, Raiders, Chargers, Buccaneers, Cowboys

4-3 High Blitz, High Zone

• Panthers, Browns, Giants, Lions, Dolphins

4-3 High Blitz, High Man

• Saints

Notes/Thoughts

• There's definitely a continuum between these categories as well as within them.
  
• A lot of the groupings were expected, but sometimes they weren't.
  
• The Steelers are famous as 3-4 zone experts. Never realized that the Redskins ran a lot of zone too. They do it with more predictability though, evidenced by the lower DB blitz percentage.
  
• The Patriots are supposedly a multiple team, but looking at these stats, they fit right in with two other pure 3-4 teams, the Chiefs and the Colts, on the basis that they rush 2-3 guys more than 20% of the time (the tops in the league). Pats, Chiefs, and Colts are top 3 in the league at this, too.
  
• There's a clear coaching tree between the Seahawks, Falcons, Jaguars, 49ers, and Raiders. It's interesting to see their differences in coverage tendencies. This probably comes down to personnel more than anything, but nevertheless, it does make for a different product on the field.
  
• 4-3 high blitzers and 3-4 low blitzers are mostly failures, it seems. The minor exceptions to that rule were the Panthers and Saints on the 4-3 high blitzer side and the Patriots and Chiefs on the 3-4 low blitzer side.
  
• High blitzing and high zone defense don't mix. Only the Steelers and Panthers get away with it.
  
• High blitzing and the 4-3 don't mix. Only the Panthers and Saints get away with it, and even then, neither has a great defense (not in the top 10). I also think the Saints run a little 3-4, to be fair.
  
• There are three things a defense can do: defend the run, rush the passer, cover a receiver. As such, there are three things a defense can do to disguise itself: vary its fronts, vary its blitzes, and vary its coverages. If you wanted to find the most unpredictable defense, by this definition, you could either look for closest to the league average or closest to 50% (depending upon which you feel is more relevant).
  
• I think DB blitz is a very interesting stat because it seems to represent a disguised blitz, front, and coverage all at once.
  
• Somehow the Cowboys didn't make the playoffs or even make too much fan fair about their defense, despite having the #1 pressure rate with 4 rushers, #7 rate with 5 rushers, #4 rate with 3 rushers, and #13 rate on DB blitzes.
  
• Likewise, the Browns had a stellar 43% pressure rate from their defense. I guess pressure isn't everything. The Browns even had the second best yards per attempt allowed as a team defense. What gives with them?!
  
• I think people tend to be biased in preferring man coverage or zone coverage, and they will label the other coverage 'stale' or something to that effect. However, universal trait of these defenses that got stale, particularly in playoff situations, was low blitzing. On the other hand, high blitzing is almost a death knell, if you run a 4-3 defense.
  
• By this reasoning, if you want to have a defense that stays varied and disguised (read: doesn't get stale in pressure situations or games), then you want an attacking defense, and you want to base that out of the 3-4.
  
• If you have a high blitzing 3-4, you better not be too biased to zone defense or have too little DB blitzing either. These also indicate too much predictability and likely a personnel group that is too inflexible.
  
• Which teams follow the philosophy that I've described, more or less? The Cardinals, Ravens, Jets, Titans, Texans, and Packers. That list is filled with a mix of great and not so great defenses. Maybe we can figure out what the differences are.
  
• The Cardinals and Ravens were the only ones with a double digit sack artist.
  
• In general, it seems like each of these teams had serious holes in terms of talent. Most didn't have two decent CBs to start.
  
• None of these teams had their best season in recent seasons, which you have to attribute to injury, bad luck, etc. The Cardinals had the #2 defense in 2016 in terms of yardage. The Texans were #1 that year. The Ravens are rarely out of the top 10 in any year, but they haven't quite peaked since back in 2011 when they were #3. The Jets were #1 overall in 2009 and #4 as recent as 2015.
  
• Another interesting feature of defense is how it relates to offense. I don't know if this is substantiated by statistics or not, but the general knowledge goes that a high powered offense will put the defense in too many bad situations because fast drives put them back on the field too quickly. A high powered offense and defense have a hard time coexisting. And when they do, there's the question of if you want one side to be aggressive and the other passive or what. There's the typical high powered passing attack with a bend/don't break D such as the Pats or Eagles last season, and there's the aggressive defense with the power rushing attack such as the Ravens or 49ers back when they had Harbaugh.
  
• There are a few examples of teams where an aggressive offense was matched with this aggressive, diverse form of defense. The 2015 Cardinals, basically any Packers team as long as Rodgers is healthy and the defense has enough talent that year (but the Packers also had peak years in 2009 and 2010), and the 2012 Texans.

Do you find any of these philosophies more attractive than others? What do you extract from this data?

A very solid article that explains, in more words, what is wrong with the bend but don't break style in the modern NFL: Interception numbers explain why Dom Capers’ Packers defense is struggling

One further note about the 3-4 type teams. When you have stand up style pass rushers, you have more front versatility in nickel packages. 4-3 teams are committing 4 man fronts, and they either have 1 or 2 edge rushers in that base front. Their odd fronts come from using a strong side backer, who is generally mediocre as pass rushing. In nickel, they'd have to keep the strong side backer on the field and have only one other linebacker. This puts the middle of the field in a very weak position. Alternatively, they could drop their 1 technique and keep the strong side backer on the field for a 3-3 look. Very few 4-3 teams have the personnel that is versatile enough to achieve this.

A 3-4 team can drop the nose, and their DTs are generally able to pick up the slack because they're already used to being 2-gap players. They can go with the 2-4 look that way. Or, they can go 3-3, and it can be either an odd or even front. In this case, again, their DL is generally more capable at run defense (not to mention the OLB/DE guy), so they aren't so handicapped.

Essentially, 4-3 base teams have to go 4-2 Even in nickel, and 3-4 base teams can go 2-4 Even, 3-3 Odd, or 3-3 Even. This is a pretty dramatic difference in versatility for a personnel package that is on the field 60-70% of the time these days.

Also of note: 4 of the top 5 defense currently are running a 3-4 base: BAL, WAS, NYJ, and LAR.

Through 2 weeks, here are the top 10 pass rushers:

1. Khalil Mack
2. Sheldon Richardson
3. Demarcus Lawrence
4. Jurrell Casey
5. Von Miller
6. Fletcher Cox
7. Mike Daniels
8. Melvin Ingram
9. Chris Long
10. Bradley Chubb

With the exception of Chubb and possibly Long (two former top 5 picks, I might add), these guys are pure 3 techs or outside edge rushers.

A 4-3 defense (even when playing in base nickel) can realistically only have 1 3 tech and 1 pure outside edge rusher on the field, unless they are willing to introduce some weaknesses and/or make substitutions at just the right times (going small when the offense passes, going big when they might not pass) along with having a deep bench.

A 3-4 defense that is built with some 1 gapping in mind can realistically have a starting lineup with twice the number of these types of pass rushers. That is to say, they can start 2 pure edge rushers and 2 3 techs. And as I alluded to in the previous post, they have the flexibility in nickel to choose what to get rid of, but they can have 4 starters on the field to produce a maximum pass rush in a Wide 9 formation. Whereas the 4-3 defense will either need all-world talent to make no subs but will more likely have at least 1-2 bench players on the field to achieve the same Wide 9.

4-3 defenses that achieve great pass rush through depth are typically one-season wonders. Injuries, salary, and other pressures prevent these talents from staying together. The Giants had about one or two elite seasons with their crew. The Jags had an amazing season last year but are falling back to Earth. The Cowboys look to be the top 4-3 defense this year. It's very cyclic teams that follow this philosophy.