What were the Buffalo Bills defensive personnel tendencies in 2019?

The backbone of the Buffalo Bills for most of 2019 was the defense. Most of us likely have a good grip on the names and faces, and a fair amount of comfort in overall scheme. Across an entire season, though, it’s tough to mentally juggle everything. Let’s dive into the data and see what groupings the Bills favored.

Fun with numbers

Thanks to the magic of the NFL cataloging nearly everything imaginable, we can give some fast facts on the defense that might shock and surprise you. Or not. Let’s find out...

• With so few injuries, it’s no surprise to see that the Bills had only 57 players take the field in 2019, which was the least in the league. There were 28 players on defense who took the field.
• Despite this remarkable player stability, Buffalo featured their most common defensive lineup only 3.54% of the time. That’s near average. Near average is somewhat odd for a team with so few players getting snaps however.
• That last thing is even more interesting if you know that the Bills had only eight different starting lineups all year.
• Even wackier, their lineup and player counts got a small boost from Isaiah McKenzie taking a few snaps at corner in Week 17.

Snap-count notes

We’ve seen them weekly, so let’s check in on the year. The entire table can be a bit too much for an article, but if you’d like the full list of snap counts it’s all readily available at Pro Football Reference.

Now that you have all the information you could ever want, let’s do some math magic to try and come up with an idea of base defense for the Bills. As a quick note on method, I added up all the snap counts based on position group and divided each total by 1,036 (the total number of snaps for the Bills’ defense this year).

A perfect 4-3 defense would break down into whole numbers using that method to give 2 defensive end spots, 2 defensive tackles, 3 linebackers, 2 corners and 2 safeties. We all know it won’t be that nice though, so here’s a graphic.

None of those are whole numbers. Time for math. Corners are listed first because the greatest deviation we’d expect from our perfect 4-3 defense is to play nickel, which would be more like a 4-2 defense. Note that these next statements will give ballpark figures as dime and quarter defenses, and other wackiness means there’s always a handful of snaps that would change some figures, but...

The 2.48 corners suggests that the Bills played nickel defense rather than a true 4-3 almost half the time. Except the Bills also like big nickel so you’d add the “extra” snaps at safety, which puts the nickel usage around ³⁄₄ of the time.

Except that’d seemingly be weird because linebackers ended up as 2.45 players, or 45% or so of the time in a 4-3. Put another way, the Bills can’t be in nickel 75% of the time and 4-3 defense about 45% of the time because that’s too many percents and there’d be a lot more too-many-men-on-the-field flags.

But of course you remember that Lorenzo Alexander played defensive end and defensive tackle quite a bit and as you might expect those positions are below 2.0 players. If you add up the “missing” partial player for those spots it comes out to 0.18 players. If we subtract that from our 0.45 partial linebacker (Alexander) assuming he filled in for the other two position groups, that gives us 0.27 linebackers actually playing linebacker.

That means the initial information was spot on. The Bills spent about 75% of their time on the field using a nickel defense. Essentially Buffalo is a 4-2 base.