by Bryan Knowles

Earlier this week, we looked at what personnel groupings were most popular on offense. Now it's time to turn around and look at things from a defensive standpoint. In a league where three wideouts has become not just the most popular formation but the default formation, how have defenses reacted?

Just as three-wide formations have become the offensive default, nickel defenses are now the NFL's primary defensive formation. Nickel first became more prevalent than base defenses in 2012, and became a majority of all plays in 2015. There's a reason the AP All-Pro team added an extra "defensive back" position in 2016; slot corners are now more likely to see the field than your seventh guy in your front seven.

Base defenses remain more effective on the whole, though that is misleading. Nickel packages are by a significant margin better at handling 11 personnel (0.8% DVOA for nickel, 8.4% DVOA for base sets), so it makes sense that that would become the most played defense. Base personnel are still better at handling things like two-tight end sets, resulting in better overall DVOA. Nickel is the best defense for defending the most popular offense, so it has become the most popular scheme

Defensive Personnel Groupings Personnel 2016 Pct 2017 Pct Difference

2017 DVOA Nickel 57.4% 52.3% -5.1%

1.1% Base 29.7% 33.1% +3.4% -3.6% Dime+ 11.0% 12.9% +1.9% 5.7% Goal Line 1.2% 1.0% -0.2% -1.5% Big 0.7% 0.7% 0.0% -0.9%

A couple quick notes here:

We no longer separate 3-4 and 4-3 fronts in our stats. In all honesty, the distinction is becoming more and more meaningless in the modern NFL; the difference between a 4-3 defensive end and a 3-4 outside linebacker is more or less whether or not they have their hand in the dirt at the snap. Hybrid defensive schemes are the name of the game now, and trying to cram 2018 defensive strategy into a 1980s framework is less than useful.

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For the record, however, 55 percent of base snaps were 4-3 defenses, and 44 percent of them were 3-4 fronts. That doesn't add up to 100 because there were a handful of 2-5s, 5-2s, and 1-6s that popped up here and there. Carolina was the only defense to never stray from their front; they were a 4-3 defense and only went to a three-man line on 26 snaps all season long, all of them in nickel defenses. At the other extreme was New England, who freely flipped between 3-4 and 4-3 defenses when they could be bothered to be in base defense at all; more on that in a moment.

"Dime+" includes any package with more than five defensive backs. That includes all your dime packages, as well as the 314 snaps in quarters and six snaps with eight defensive backs on the field, all Hail Mary defenses in the last 14 seconds of halves. Half-dollar defense? Sacagawea? Paper currency?

"Big" defenses are 4-4-3 or 3-5-3 lineups, while "Goal Line" includes all other personnel groups with fewer than four defensive backs. More than half those defenses were used on the 1-yard line, but that wasn't a literal necessity; the Texans actually used it once in the other team's red zone.

As one might expect, the rise in nickel on defense is directly related to the rise in 11 personnel on offense. There's a 0.95 correlation between the two; it's a fairly obvious decision to put extra cornerbacks on the field when your opponents bring out the extra wideouts. When the frequency of 11 personnel dipped this season, so did the frequency of nickel.

That doesn't mean that every 11 set is matched with a nickel defense, of course. Last season, 74.2 percent of 11 sets were met with nickel. Dime+ packages were used 18.6 percent of the time, while base defenses actually ticked up by half a percentage point to 7.2 percent. Base defense use against 11 had been holding steady at about 6.5 percent for the previous three seasons. My hunch is that this a charting anomaly; that the rise of the hybrid linebacker/safety is being handled slightly differently by different charters. That's something to keep an eye on in future seasons.

On offense, every team used the same personnel grouping the most, with 11 being predominant everywhere. That was not true on defense, however; while nickel sets were the most predominant personnel groupings for 23 teams, there was variety throughout the league. There's really no way to talk about this without giving a massive data dump, so here's all 32 teams, with the percentage of time they spent in their base, nickel, and dime+ packages.

Defensive Personnel Frequency Team Base Rk Nickel Rk Dime+ Rk CLE 66% 1 31% 29 1% 27 LAR 58% 2 37% 25 2% 23 CAR 50% 3 49% 20 0% 32 IND 42% 4 44% 23 11% 14 DEN 41% 5 27% 32 30% 5 PIT 38% 6 36% 26 24% 7 HOU 38% 7 34% 28 24% 8 NYJ 37% 8 53% 18 8% 16 MIA 36% 9 60% 14 1% 25 SF 36% 10 45% 22 15% 10 TB 36% 11 62% 11 0% 30 OAK 35% 12 57% 16 7% 17 WAS 34% 13 63% 10 2% 24 JAX 33% 14 66% 6 0% 29 BUF 33% 15 66% 5 0% 31 BAL 30% 16 40% 24 28% 6 Team Base Rk Nickel Rk Dime+ Rk CHI 30% 17 64% 9 5% 20 CIN 30% 18 67% 4 1% 26 TEN 30% 19 64% 8 5% 19 DET 29% 20 52% 19 15% 11 NYG 29% 21 60% 15 11% 13 SEA 29% 22 68% 3 3% 21 KC 27% 23 29% 30 42% 3 ARI 27% 24 65% 7 7% 18 PHI 27% 25 60% 13 10% 15 LAC 26% 26 27% 31 46% 1 DAL 25% 27 55% 17 20% 9 ATL 24% 28 72% 2 2% 22 NO 23% 29 61% 12 13% 12 GB 23% 30 34% 27 42% 2 MIN 21% 31 77% 1 0% 28 NE 15% 32 48% 21 37% 4 Avg 33% -- 52% -- 13% --

Using the phrase "base defense" to describe New England's front seven is sort of awkwardly inaccurate. Not only did they freely flip between three- and four-man fronts, they rarely even had a front seven to speak of. We've seen teams use base defense less frequently than this -- New England did so in 2016, as did Green Bay -- but the 2017 Patriots stand out as the only team to go nickel-dime-base, in descending order.

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Joining the Patriots as teams that laugh at the phrase "base defense" were the Packers, Chiefs, and Chargers. Their base defenses were, in actuality, dime packages. In general, we're talking about three safeties and three corners, rather than going with four cornerbacks -- Green Bay called it their "Nitro" package -- but it's something that's growing in popularity around the league. When you're weak at linebacker depth, going with an extra safety like Morgan Burnett or Adrian Phillips in the box makes a lot of sense. The hybrid safety/linebacker position is only growing in popularity, which makes nickel formations all the more enticing.

Cleveland was the polar opposite to New England, in so many ways. The Browns stuck in their base defense 66 percent of the time, which insane in the modern NFL. You might think that this is what happens when you are constantly facing opponents running out the clock on your way to 0-16. Except that the Browns were doing this from the very start of the game! In the first half, the Browns were in base defense 66 percent of the time. When the score was tied or the Browns actually had a lead, the Browns were in base defense... the same number, 66 percent of the time.

Cleveland was the only team in the last four seasons to even hit 60 percent. This may go part of the way to explaining why they were fourth in rushing defense and 26th in passing defense; if you never go into nickel or dime packages, you're going to have trouble stopping receivers in the modern NFL! Cleveland had 245 snaps where their base defense was matched up against 11 personnel; only the Panthers and Rams joined them above 100. To put it another way, roughly one-sixth of all 11-versus-base snaps in the NFL were played by the Browns defense. At least they were unique!

The Rams were the only other team to use their base defense more than half the time, though Carolina missed out on joining them by just four plays. Carolina only had 10 plays not in either base formation or nickel, and nine of those were at their own 1- or 2-yard line. As mentioned earlier, every single one of Carolina's base sets was a 4-3 front, so no team in the league had as little defensive variety as Carolina. That sounds like my kind of defense, by which I mean the kind of defense I would literally design because I am neither good nor creative at designing defenses. For all that, Carolina ranked seventh in defensive DVOA, because when you have Luke Kuechly, Thomas Davis, and Shaq Thompson as your linebackers, you can get a lot of versatility without actually having to sub anyone.

Minnesota, Atlanta, Seattle, and Cincinnati were the least balanced defenses in the league, sitting in nickel more than two-thirds of the time. Contrast that with Houston, Baltimore, and Pittsburgh, who didn't use any defensive personnel package more than 40 percent of the time, freely flipping between base, nickel, and dime packages depending on what personnel the offense trotted out.

It's interesting that even with the homogenization we've seen in personnel packages on the offensive side of the ball, there are still so many different ways that defenses choose to handle it. It's not like there's an obvious right or wrong way to do it, either -- the Vikings, Ravens, and Rams were about as far from one another as you can possibly get, yet all three were in the top six defenses by DVOA.

It doesn't seem to matter whether you stick to what you're best at or substitute to match every single variation offenses put out there. Either can work -- as long as you have the talent to back it up.