How do NFL defenses survive in a game that favors offense?

The deck’s stacked against defenses in today’s NFL, so to have an impact, teams are having to reassess what they want a defense to do.

Defense is hard as hell to play in the NFL now.

Rules are slanted in favor of the offense more than ever, so teams are more apt give up tons of points or hundreds of yards — that’s an inescapable fact of the current NFL landscape. Defense still matters, but teams have had to reprioritize what they want a defense to do.

It’s more than just stopping the offense from moving the ball. Defenses have to mitigate the advantages offenses have now by playing their own style of explosive football, specifically creating turnovers, sacks, and tackles for a loss. Those represent negative plays that force an offense to lose yards and put them in a more difficult positions or lose possession entirely.

Sacks, tackles for a loss, and turnovers may not match, apples to apples, the big plays an offense can produce (defined here as gains of 20 or more yards), but these defensive big plays help teams slow down offenses and set up their own team to score.

But how do you quantify defensive value in today’s NFL? How much exactly are they worth to a team’s overall output on the field?

To attempt to put a value of those plays, we used numbers that quantify expectations, including points per drive and average field position. With that information, we can see that focusing on explosive defensive plays is the best way to play defense in a league that’s making defense harder than ever.

What numbers are we using and what can they tell us about the value of defensive play?

To understand a team’s performance, it helps to put it in the context of the NFL average for a statistical category. That way, we can see how teams are performing relative to what they’re expected to do.

Let’s start with sacks as an example. To find out how many sacks a team is above or below the NFL average on a per dropback basis, subtract the league average sack percentage from the team’s own sack percentage, then multiply it by the amount of total dropbacks they’ve faced.

Let’s use the Cardinals as an example. Through the first 12 weeks of the season, they had a sack percentage of 9.5 percent — tops in the league. The league average is 6.7 percent.

• 9.5 percent - 6.7 percent = a sack rate 2.8 percentage points higher than the league average.
• 2.8 x 389 total dropbacks faced = 10.79 sacks better than the average team.

We can use the same method for tackles for loss and turnovers to figure out which teams are the best at creating the defensive equivalent of explosive plays.

When sacks, turnovers, and tackles for loss created are measured against the amount of points allowed per drive, the correlation is pretty strong.

Making plays in the backfield and creating turnovers is how to play defense in 2018

Adding together the expected sacks, tackles for loss, and turnovers can give us one number for the amount of explosive plays that defenses are expected to make. If the number is negative, that means a team is below average.

Here are how all 32 defenses stack up in terms of points per drive numbers, sacks, turnovers, and tackles for loss versus expectation. Points per drive is just the average amount of points a team scores (or in this case, gives up) every drive they’re on the field.

Taken individually, the correlation for sacks, tackles for loss, and turnovers to points per drive is pretty low. But putting them all together yields a much stronger result.

The stronger a correlation is to 1 or minus-1, the stronger it is. The closer to zero, the weaker it is.

• Sack % Expectation to Points Per Drive: minus-.404 correlation
• Turnover % Expectation to Points Per Drive: minus-.337
• Tackle for Loss % Expectation to Points Per Drive: minus-.280
• Sacks + Tackles for Loss + Turnover % Expectation to Points Per Drive: minus-.502

When you pair sacks, tackles for loss, and turnover percentage expectation with average starting offensive field position, you get a correlation of .296. Using just turnover percentage expectation with average starting offensive field position, the correlation jumps all the way to .662 — defenses need to make big plays to help their offenses.

Playmaking defenses help set up offenses with great field position

One of the most interesting teams on the list is the Baltimore Ravens, who don’t really get a lot of turnovers, but still play a suffocating brand of defense. The Ravens are 31st in turnover percentage, yet they lead the league in yards per play and open play success rate.

(Note: The stats below are through Week 14.)

Even though the Ravens don’t get a lot of turnovers, they still set their offense up with strong field position. Baltimore’s offense ranks 11th in average starting field position, which undoubtedly helps a unit that’s last in the league in big-play rate.

The Houston Texans and Chicago Bears are in a similar boat. Both of these defenses excel at creating explosive defensive plays, and their offenses largely benefit from it. Based on open field success rate, the Texans (24th) and the Bears (21st) lack consistency down-to-down, but they do get great average starting field position. The Texans offense has an average starting position of 31.3 yards (second in the league) while the Bears average starting position is 29.3 yards (sixth). It’s no surprise that these offenses get to start in advantageous positions considering how well their defenses get sacks, turnovers, and tackles for loss.

The Saints rank fourth in sacks, turnovers, and tackles for loss expectation, but they only rank 22nd in points per drive. In other words, the New Orleans defense right now is reliant on creating big plays because it hasn’t found consistency on a down-to-down basis. It also helps that the Saints have a rock-solid red zone defense.

It’s a volatile style of defense for sure, but it has worked well for New Orleans this year. The Saints’ offense ranks first in average starting field position at 31.9 yards. They’re averaging 6.2 yards per play (fourth in the NFL) and 34.9 points per game (second in the NFL). Giving one of the best offenses in the league advantageous starting position allows them to be more potent.

Their loss to the Cowboys in Week 13, when they only scored 10 points, was a bit more traditional as far as the NFL goes. However, those games becoming increasingly rare — there have only been 16 games this season where the combined point total was fewer than 23 points. Holding offenses, especially offenses like the Saints, to that kind of output on a routine basis isn’t going to happen.

It’s not exactly groundbreaking analysis, but defenses still need to be able to make plays when they aren’t slowing offenses down.

What about the Rams and the Chiefs?

Both of these teams are the best in the NFL when it comes to generating offensive big plays, and they’re two of the most explosive offenses overall. That was clear in the Rams’ 54-51 win over the Chiefs in Week 11.

However, their defenses are another story. They don’t create many big defensive plays, and they both rank in the bottom 10 for points allowed per drive.

The Rams do have a wrecking ball on defense, Aaron Donald, who can completely change the course of a game. Against the Chiefs, Donald had two sacks and two forced fumbles. One of those forced fumbles was picked up for a score. The other one set the Rams up at the Chiefs’ 46-yard line, a drive that ended with another touchdown.

On the flip side, Donald had a quiet game in a 15-6 loss to the Bears in Week 14.

Even if the rest of the Rams’ defense isn’t as consistently dominant as Donald is on an individual level, having a guy who singlehandedly turn the tides by making big plays helps. Those two plays were as crucial to the Rams’ three-point win as anything the offense did.

The Chiefs and the Rams, even with Donald, have typically been offense-reliant this season, but they’ll likely need some big plays from their defense to advance in the postseason — even if they aren’t consistent on a play to play basis.

The old phrase “defense wins championships” means something much different now than it used to. The last two Super Bowls had 62 and 74 combined points scored. In 2016, both the Falcons and the Patriots met as offensive juggernauts in the Super Bowl. The same can be said about the Eagles and the Patriots last season.

The eventual winners in those Super Bowls also got big plays from their defense. Brandon Graham’s late-game strip sack of Tom Brady erased New England’s chance at comeback in the Eagles’ first ever Super Bowl win. The year before that, Dont’a Hightower’s strip sack against Matt Ryan set up the first of two fourth-quarter touchdowns on the way to the Patriots’ overtime win.

How the defense came through for the team wasn’t by NOT giving up points and yards; it was by creating their own explosive plays to stifle opponents and set up their own offenses. Sacks, tackles for a loss, and turnovers are all ways the defense helps the offense. So the good news for high-octane offenses like the Rams and Chiefs is that offense wins championships — as long as defenses contribute with big plays.