The Case for the Zero Blitz
Guest column by John Shirley, Sports Info Solutions
Why Teams Should Blitz More
Blitzing allows defenses to play downhill and dictate to the offense instead of sitting back and being forced only to react. Blitzing is also the quickest way to increase pressure on the quarterback. The following chart illustrates this, showing that pressure rate understandably increases as more rushers are added. * All data used is courtesy of Sports Info Solutions and from the 2016-2018 NFL regular seasons, unless otherwise noted.
The more defenders rushing the passer, the more pressure a defense gets on opposing quarterbacks. And pressure is the defense's best weapon against this era of pass-happy offenses. The following graph shows just how drastic of an impact pressure can have on how offenses perform by Expected Points Added (EPA).
Just hurrying the quarterback drops the average EPA allowed per dropback from 0.21 to 0.04, with increasing pressure levels dropping it even further.
The Zero Blitz
Given the above reasons to consider aggressive blitzing, we can show why the Zero Blitz (Cover-0 Blitz) in particular is something that defenses should utilize more often. For this analysis, blitz schemes were split into three different buckets: Zero Blitz, Zone Blitz, and Man-Free Blitz (Cover 1 coverage with 5+ rushers). These three blitz types were compared by EPA per Dropback, Positive% Allowed (the percentage of plays in which the defense allowed an EPA above 0.0), and Boom% Allowed (the percentage of plays in which the defense allowed an EPA of 1.0 or more). All following statistics exclude plays from within the defense's 10-yard line since strategy changes heavily once a defense is backed up against its own goal line.
|Defensive Performance by Blitz Type|
As shown above, the Zero Blitz is generally the most effective blitz scheme of the three categories. It has the lowest average EPA Allowed and Positive% Allowed. The most surprising part is that it also has a comparable Boom% Allowed. The Zero Blitz is the only blitz type that has no deep safety, so it would be assumed that it allows a higher percentage of big plays. However, it actually allows basically the same Boom% as any other blitz. This absence of any deep safety allows for Zero Blitzes to average about one extra pass rusher per play. As shown earlier, more pass rushers equals more pressure on opposing QBs.
The graph above shows just how much more efficient at creating pressure Zero Blitzes are when compared to other blitz types. While Zero Blitzes do have a slightly lower sack rate, they have a higher percentage of every other pressure type and an overall higher pressure rate of 50 percent.
Zero Blitz vs Man-Free Blitz
If the Zero Blitz is so effective, then why is it called so infrequently? It is consistently the least-called blitz (7 percent of all blitzes in 2018), while its more conservative man coverage counterpart, Man-Free Blitz, is consistently the most called (53 percent of all blitzes in 2018). This is most likely because coaches are generally risk-averse and blitzes with an extra rusher and no safety help are seen as feast-or-famine play calls. Man-Free Blitzes are considered a safer play call since they have a deep safety present who is there to clean up any mistakes and help in coverage. But does the presence of a deep safety actually help a defense? Based on SIS charting data, deep zone safeties were only involved in 8 percent of Man-Free Blitzes in 2018. Being involved includes making a play on the ball, helping in coverage on the targeted receiver, or being involved in a tackle. So, it seems that a single high safety is extremely limited in the amount of plays he can be involved in and might not be the safety net that he's assumed to be. Evaluating single-high safeties shouldn't be just about how many plays they can be involved in, though. The presence of a deep safety can also deter targets to the deep middle of the field (between the numbers and 15-plus yards downfield) and make life harder for opposing quarterbacks. This is proven partly true in the following table, which compares Man-Free Blitzes to Zero Blitzes on pass attempts only (excludes scrambles and sacks).
|Zero Blitz vs. Man-Free Blitz Performance|
|Blitz Type||Attempts||Avg. Throw
It is true that Man-Free Blitzes do a better job at deterring targets to the deep middle part of the field, although it is only an improvement of 1.3 percentage points. It is striking how well Zero Blitzes stack up even when sacks are excluded, and those extra deep middle throws may not be such a negative.
|Zero Blitz vs. Man-Free Blitz Performance on Deep Middle Throws|
There isn't much of a sample size for deep middle throws against Zero Blitzes, but the few results we have compared very well to those same throws against Man-Free Blitzes. It would be interesting to see how a larger sample size might affect these numbers to see if Zero Blitzes would continue to have more success.
Criticisms of Increased Blitzing
The criticisms of aggressive blitzes are the risk of allowing a big play (which the data so far suggests to be a false assumption) or that a quick passing game can nullify the pass rush. It has been shown already that Zero Blitzes allow a similar Boom% to other, more conservative blitzes, but how do they compare to other defenses when they fail to create pressure? As it turns out, about the same. On 269 clean-pocket pass attempts, Zero Blitzes averaged +0.24 EPA allowed and a 54 percent Positive%. This is basically the same as the average clean pocket attempt against all defenses -- +0.23 EPA allowed and a 55 percent Positive% allowed. A quick passing game seems like a logical counter to the Zero Blitz, but the numbers don't quite bear that out. On 42 pass attempts faced from a zero- or one-step quarterback drop, Zero Blitzes averaged -0.14 EPA allowed and a 43 percent Positive% allowed in 2018 (drop type data only exists for 2018). Once again, the Zero Blitz is extremely effective, but also in a small sample. To increase the sample, let's look at how Zero Blitzes performed against short passes (5 or less yards downfield). On over 239 short pass attempts from 2016 to 2018, Zero Blitzes averaged only -0.05 EPA allowed and a 48 percent Positive%. It seems that a quick passing game isn't quite the counter to the Zero Blitz that it's expected to be.
Hopefully this analysis shines a light on just how effective blitzing—the Zero Blitz in particular—can be at disrupting an opponent's passing game. Unsurprisingly, creating pressure on the quarterback is a major factor in this, and the Zero Blitz has shown to be the best at doing so, since it allows for an extra pass rusher. The fascinating aspect is that this aggressive blitz isn't as risky as it is assumed to be, allowing a similar big-play percentage as its more conservative counterparts. If defenses want to start dictating play to the offense, the evidence points to further utilization of the Zero Blitz.