It’s time to change the way we talk about NFL defensive systems

Back in October I wrote an article about the flawed way offenses in the NFL are described by analysts. Media members have a tendency to tell you about how NFL offenses were decades ago rather than accurately portray what is happening in today’s NFL with their West Coast Offense, Air Coryell, and Erhardt-Perkins labels.

The Jets’ hiring of Gregg Williams has served as a reminder that this is not limited to offense. Analysis of defense is also weighed down by outdated descriptions.

Much time and attention has been provided to the Jets changing from the 3-4 system of Eric Mangini, Rex Ryan, and Todd Bowles to the 4-3 system of Gregg Williams.

But it isn’t quite that simple. In the modern NFL, these labels have become largely obsolete.

Perhaps the biggest issue is that today’s NFL doesn’t make it practical to run a 4-3 or a 3-4 as a base defense. By definition a 4-3 defense has 4 defensive linemen, 3 linebackers, and 4 defensive backs. A 3-4 defense has 3 defensive linemen, 4 linebackers, and 4 defensive backs.

The rise of the modern passing game has greatly reduced use of these personnel packages on defense. When offenses regularly put 3 or more receivers on the field, defenses cannot play only 4 defensive backs. At least 5 defensive backs are necessary on most plays, which means removing at least 1 lineman or linebacker. That means the defense becomes something other than a 4-3 or a 3-4.

Consider this.

Over the last two seasons Vance Joseph’s Broncos had their “base” package with 4 defensive backs on the field more than any team in the league, and they still used it less than half the time.

But even if we assume this isn’t true, there are other ways these rigid labels no longer work.

Beyond the way personnel groupings are dictating things, offenses have become more and more sophisticated over time. Every defensive playcall has weaknesses. If you are running the same thing over and over on defense, modern offenses will know exactly how to attack it and eat you alive.

As a result, virtually every defense in today’s NFL has to mix up its defensive looks over the course of a game. That includes its fronts.

Let’s take a look at some of the fronts from the Week 3 game between the Jets and Browns. We can compare “3-4 Todd” Bowles and “4-3 Gregg” Williams.

We will start with some of the looks the Jets showed.

In this expertly drawn box we can see “3-4 Todd” went with a 3 defensive lineman look. No shock there.

But then this expertly drawn box shows “3-4” Todd with a 4 defensive lineman front.

Things get back to normal in this expertly drawn box as the defense of “3-4 Todd” has 3 linemen.

But yet again “3-4 Todd” had 4 defensive linemen in this expertly drawn box.

Now let’s switch to “4-3 Gregg.” This expertly drawn box shows the Browns with 4 defensive linemen.

But then this expertly drawn box shows “4-3 Gregg” with only 3 defensive linemen.

Things get back to normal with “4-3 Gregg” in this expertly drawn box as the Browns have 4 defensive linemen.

But then “4-3 Gregg” only has 3 defensive linemen in this expertly drawn box.

By the way, every single one of those shots came in the first quarter of the game the Jets and the Browns played. Hopefully they show how the fuss between 4-3 and 3-4 is vastly overrated in today’s NFL.

There was a day where clear distinctions existed between 3-4 and 4-3 defenses.

Many 3-4 scheme in the past asked their linemen to cover 2 gaps (spaces between offensive linemen). The job of these linemen wasn’t penetrating. It was really to tie up blockers so that linebackers were free to make plays.

One of the advantages of the scheme came from the standard 4 man pass rush. In addition to the 3 linemen, the fourth pass rusher could be any of the linebackers. The offense had no idea which one it would be before the snap.

A team that ran a 4-3 in the past might assign each lineman a single gap and ask the other gaps to be taken by linebackers (and/or safeties). The linemen could penetrate and make plays. While it was usually more predictable, it gave the chance for big, elite athletes to make more impact plays since their job was to get into the backfield instead of tie up blockers.

There was a point in time when few teams ran a 3-4, which arguably gave those teams an advantage.

Star caliber defensive linemen who consistently penetrate and make impact plays are hard to find. Linemen who are strong enough to fill two gaps and hold up at the point of attack aren’t as difficult to acquire. Furthermore, with most of the teams in the league running a 4-3 at that point, these stout gap fillers weren’t useful to most of the league and thus could be obtained cheaply. The same goes for pass rushing 3-4 outside linebackers. These tended to be athletes who weren’t big enough to hold up as 4-3 defensive ends. With most of the league running the 4-3, these guys weren’t in demand, but they fit the 3-4 well.

The classic 2 gapping 3-4 defense has largely gone out of style. While some teams have a single linemen or even a couple 2 gap, you’d be hard-pressed to find a team that asks all of its linemen to do so for most of the game. I would argue that the rise of the modern passing offense again has something to do with it. As the passing game has continued to grow in importance, defenses have put more of a priority on rushing the passer, which requires more penetration through a single gap and puts less of a premium holding the point of attack to contain a pair of gaps.

A lot of looks that are nominally 3-4 in today’s NFL have responsibilities that resemble a classic 4-3.

This isn’t entirely new either. Wade Phillips has run his defense like this for decades.

So in many ways the only functional difference between a 3-4 and 4-3 is whether an edge guy has his hand on the ground. If either edge guy in the picture below just got into a 3 point stance, this would be a 4-3 look. Since neither does, it’s a 3-4 look. But there really isn’t any difference otherwise.

In conclusion, the whole 4-3 vs. 3-4 thing is overblown.

I keep seeing people talk about scheme fits. For example, I see discussion about whether a pass rusher is an option for a 4-3 team because he projects more as a 3-4 outside linebacker. This is flawed thinking. In today’s NFL quality edge rushers are an extremely valuable commodity. It shouldn’t matter whether that edge guy is more comfortable standing up as a linebacker or putting his hand on the ground as a defensive end. Your team should be able to accommodate him.

When we talk about scheme, we should think about blitz rates, utilization of man vs. zone, most common coverage shells, and the roles that need to be filled within the system.

4-3 and 3-4 have become largely obsolete labels.