The best indoor running defenders probably won’t improve your defense
The battle between running blockers on the offensive line and running blockers on defense has defined the NFL for decades. But, in 1994, the league changed his rules to encourage passing and turned football from a sport largely decided in the trenches into a sport decided in the air. Along the way, the league that averaged 18.7 points per team game in 1993 turned into an average of 24.8 points per team game last season – an all-time record.
But despite the modern proliferation of overtaking, the art of running and stopping is far from dead. NFL teams always enjoy running defense, and many continue to invest in skilled inside defenders to close running lanes. Washington inside defensive lineman Daron Payne was the 13th overall pick in the 2018 draft, and the New York Jets took Quinnen Williams third overall in 2019. Each is a talented and tall man who can play in different positions along the line and possesses the ability to rush,1 but both are primarily intended to help their teams defend the race.2 Obviously, teams think it’s important to stop the race, otherwise they wouldn’t spend premium picks to acquire players who are adept at this skill.
Given that belief, we were curious as to which teams were best at stopping the opposing ball carrier and how much that actually matters. Specifically, we wanted to measure whether a good interior defense of the race helps to win football matches. Does the indoor running defense have an impact on how many points a team awards? Does a strong inside line encourage the other team to pass more and, by extension, gain more yards?
In trying to quantify running defense, we relied on the work of ESPN analyst Brian Burke, who introduced the “run stop win rate”Metric last year. Its metric is based on NFL player tracking data from 2017 to 2019 and is calculated using “angles, distances and speeds throughout a game’s execution to tell who is blocking whom and for. determine if the defender was able to significantly beat the block (or blocks in the case of a doubles team) on the designed racing games.
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“Run stop wins” is a promising measure. Burke reports that on average, the opponent’s rushing efficiency decreases as the number of stoppages a team wins on a play increases, indicating a well-calibrated measure of defensive performance. Our new metric takes the metric developed by Burke and the ESPN analytics team, and adjusts for two things over the course of a season:technicalhe played. Techniques are basically the roles the lineman has been asked to play along the defensive line. For example, a “zero technique” means the lineman will stand directly over the center , while a “technique three” means he’ll settle down somewhere in the gap between the guard and the tackle.
We adjust the techniques played because an inside defender lined up directly over the center (zero technique) tends to gain more stoppage wins per 100 snaps than players asked to line up directly with the guard ( two-man technique) or tackle (four-man technique).3 And since snap volume has a big influence on how many stop-run wins a player can expect to earn, we’re adjusting that as well. After finding the expected stoppage gains for each technique, we aggregated the expected run gains per player, calculated each defender’s gains above or below expectations, and then summed them up by team.
We call our new metric “predicted run stop wins over” (RSWOE). According to him, the New York Jets had the best home defense in the NFL in 2020 – and it wasn’t even close. Led by Williams’ 36.9 RSWOE, which is the highest of any indoor lineman in a season since 2017 (when player tracking began), the Jets topped the field, adding more than twice more wins to the point than the second-placed Los Angeles Rams.
On the other end of the spectrum are the Minnesota Vikings, sitting nearly 200 RSWOEs behind the Jets. Shamar Stephen (-50.7) and Jaleel Johnson (-28.5) paved the way for defensive racing futility for Minnesota, with Stephen’s incredible 50.7 wins under ranking expected as the worst of an NFL season since 2017. Indeed, Stephen’s poor play against the race was notable for its consistency: Stephen has three of the 16 worst playing seasons of the past four years (according to RSWOE) , which makes him by far the biggest liability in the league against running among indoor linemen.4
An important note here, however: there is no clear pattern that emerges between RSWOE and many other measures of defensive performance. When we look at its correlation with allowed defensive points or the team’s scoring margin, for example, hardly any relationship exists. Being good at stopping the run doesn’t seem to help defenses keep attacks from scoring, and being bad doesn’t seem to hurt in this effort.
Digging deeper, a team’s RSWOE holds a weak but positive correlation with the added expected points it allows per play. And since a negative EPA per play is good for a defense, a positive relationship between the two indicates that the higher the RSWOE, the more less efficient defense is global. We see a similar story with a defensive success rate, although it has an even stronger correlation in the wrong direction. Defensive success rate measures the share of games in which a defense prevents an attack from gaining added expected positives. (For example, a defense holding an offense with a gain of 2 yards on the second and 5 would be considered a success by this metric.) Higher numbers are better for the defense, so a negative correlation means we’re still seeing that the stronger the interior. running defense, the poorer the overall defensive performance.
|metric||corr with the expected victories|
|EPA / set||0.08|
|Margin of points||0.02|
|3rd low conv. %||0.01|
|Def. success rate||-0.17|
|Peak Course% Offensive||-0.26|
Meanwhile, the strongest correlation tested suggests that the more dominant the indoor running defense, the more an opponent will back down to pass – and the less they will try to run.5 In some ways, this is the expected result: Rational callers avoid strong interior lines by passing more. Yet defenses also tend to suffer when channeling the opposing offense more into the passing game, as passing the ball remains more efficient than to run it.
This takeaway can upset teams who have invested heavily in stopping domestic linemen. But for these teams, it’s worth considering whether tricking your opponent into using their most effective type of play against you is a suboptimal strategy. Unless your defense is dominant in all facets of the game, making your opponent run more – and pass less – will likely be a better approach. Because at the end of the day, in a league structured to reward teams that throw early and often, daring to pass your opponent is probably a recipe for disappointing results.