Identifying Pass Defenses Case Study: #ITPFilmRoom02

Reading defensive coverages is not an easy task. In fact, without knowing the call, even professionals may disagree (as with many things football). David Archibald takes a look at the process – and difficulties – of understanding what we see in the film.

Thanks to the efforts of The Reverend James Mastrangelo (@thereverendum), Inside the Pylon recently introduced #ITPFilmRoom on Twitter. Periodically our Twitter account will show the early stages of a play and invite the audience to guess what happens next.

The second entry in the series, featuring Michigan State’s offense squaring off against the Stanford defense, proved somewhat controversial. Even after multiple viewings, no one could quite seem to agree on what the defense was.

The play in question:

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The clip was intended to highlight Stanford’s blitz action up front, where they put six defenders on the line of scrimmage and ran a cross stunt while dropping two into coverage. As dialogue continued, both in the ITP Slack and on Twitter, viewers found themselves more interested in what the back end of Stanford’s defense was doing. Initially we diagnosed the Cardinal D as a Cover 2 shell, but further discussion led us to revise it to Cover 4. Identifying pass defenses can be tricky.

To get a clearer answer, we enlisted the aid of some NFL contacts. One NFL coach concurred with the Cover 4 diagnosis:

ITPFilmRoom2 C4

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Cover 4 seems like an adequate explanation for the boundary (far) side, where the cornerback and safety both take deep zones with a linebacker defending the flat. On the field side, things don’t square as neatly with quarters, as the end zone view shows:

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The cornerback and nickel safety both take man-to-man turns. The man turn by the outside corner is common for Cover 4, where there’s no guarantee of inside help, but the slot defender is another matter. He should be covering the underneath third to that side of the field, but he doesn’t look to the quarterback, he doesn’t drop to a landmark, and he doesn’t pass off the receiver as he runs upfield. The deep safety plays over the top of the slot defender and never looks to the outside, as the end zone view shows. In a traditional Cover 4, he might be expected to help on in-breaking routes from the outside receiver, but he doesn’t have the depth to help, nor does he appear to give any consideration to what the outside man is doing.


[dt_divider style=”thick” /]Combination Coverage

We asked another NFL coach, who suggested that Stanford was running a hybrid coverage, incorporating different elements in the underneath coverage and deep coverage and also between the boundary and field sides (quote lightly edited):

To me the coverage looks like a version of what some people would call cover 5 or bracket coverage. It is essentially match- up combination coverage with certain in-out coverage exchange principles in the under -coverage and, based on formation and game plan, is split-field coverage principles in the over coverage. That could be Cover 2, Cover 4, or dedicated double-team principles there.

There’s a lot to unpack here.

Breaking it down, the coach is describing the following elements:

  1. The defense uses “split-field coverage principles”: There are two deep safeties dividing the field in two, as in standard Cover 2 or Cover 4 defenses. When diagnosing pass defenses, it’s generally most helpful to look at the deep safeties first.
  2. It is a “combination” or “hybrid” coverage: Many basic defenses use the same coverage pattern on both sides of the field, but modern complex defenses will often uses different defensive looks to each side, mixing both man-to-man and zone principles. Since this look has two deep safeties, the obvious coverages would be Cover 2 and Cover 4, but we could also have a man-to-man concept with the safety playing a “bracket” or a double-team to help an underneath defender with a difficult matchup.

Combination coverages are complex as a whole, but the individual assignments are similar to more vanilla defensive looks. For instance, a “thumbs” assignment to one side of the field asks the players to that side to play Cover 4 principles and is no more or less difficult than a typical Cover 4 assignment. The one exception is how the defense must react to “crossers,” receivers who start on one side of the field and run to the other. These crossers might break the coverage rules on the destination side, so the middle-of-the-field defenders must account f or them.

If the overall coverage scheme contains different concepts on each side of the field, we must break down the sides individually. The defenders on the field side appear to be covering man-to-man. The outside cornerback is in “solo” coverage – on an island with no safety help – while the slot defender and field safety work a “bracket” or double team on the slot receiver.

ITPFilmRoom2 Bracket Twins

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The interesting side is the boundary side, which is where quarterback Connor Cook (#18) ultimately attacks. The coach’s take (again, lightly edited, with my comments interspersed):

What is confusing is the boundary coverage triangle between the linebacker, cornerback, and deep safety. It looks like the linebacker communicates something with the corner pre-snap. With that tight split by the boundary wide receiver and the running back offset wide, a typical cover 5 call would be to zone off a switch release between running back flare and inside stem with the deep safety playing tight half over the top. Because there’s only one vertical threat on that side, and the safety has depth pre-snap, he doesn’t need to backpedal like his life depends on it. Essentially a version of a “triangle bracket”, making it match up cover 2.

There are a lot of ways that an offense can attack a defense, and the defense must prioritize what they want to stop. The defense can get clues as to the offense’s attack plan by looking at the alignment and formation of the offensive personnel. In this case, the boundary receiver has a “tight split,” meaning he is lined up closer to the left tackle than normal, and not far from the running back to his side. From this look, the defense must be concerned with “rub” or pick routes, where the receiver and back cross. To combat picks, the cornerback and linebacker might have a pre-snap signal for “switch release,” where the corner would take the running back and the linebacker would cover the receiver if the players cross.

Exchange vs No Exchange

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A linebacker on a receiver is far from ideal, but that is where the deep safety comes in. If there are multiple vertical threats in a safety’s area, he must get enough depth to defend either, but there is only one receiver on the line of scrimmage in this instance – he can be aggressive assisting over the top.

The cornerback jumps outside immediately on snap as if he’s going to exchange, the linebacker doesn’t flip his hips to get under the receiver, and instead matches the running back’s flare/wheel. And, worst of all, the safety is aligned very deep, is backpedaling 100 miles an hour for no reason, and is staring at the quarterback the entire time instead of getting any sort of vision on the receiver. So it looks like some version of a designer call to me. That may not be how they teach it, but I’d be willing to bet money, at least one person out of those three into the boundary straight up busted with alignment, assignment, eyes and/or technique.


Cornerback Wayne Lyons (#2) and linebacker A.J. Tarpley (#17) aren’t on the same page with respect to their coverage assignments. Lyons shuffles outside before taking his zone turn, like he is watching for the running back attacking the flat, leaving him too far outside to defend the receiver’s inside stem. Meanwhile, the Tarpley never gives any indication of helping on any receiver other than the back.

Safety Ed Reynolds (#29), already 13 yards deep at the snap, backpedals to a depth of 22 yards as the play develops. That leaves a huge hole inside Lyons and in front of the Reynolds, and Cook hits Tony Lippett (#14) for a 24- yard gain. With Lippett the only vertical threat on his side, Reynolds should have played him more aggressively.

Second Receiver Through the Zone

Note that the linebacker carries the wheel route from the running back to the boundary side. We could interpret this as indicating man coverage, but it is a very common adjustment in pattern match zone schemes to prevent the offense from using “enter-exit” principles to get a big gain. The outside receiver is trying to clear out the deep defender so the running back can attack the vacated zone with a wheel route. In Coaching Football’s 46 Defense, Rex Ryan talks about the importance of the underneath defender covering the “second receiver through the zone” to combat these kind of zone-beater concepts:

46 defense pg 101 750

Wrap Up

This installment of the film room series highlights many of the wrinkles in modern combination coverages. Defenses have the ability to tailor their assignments to combat the threats offenses present. This versatility presents challenges for opposing offenses, who must diagnose the coverage. However,but it also requires that all 11 defensive players understand their assignments and any adjustments or coaching points they must make in response to the offense. In this instance, the Stanford defense might have outsmarted itself, leading to a significant gain for the Michigan State Spartans.

Follow @davearchie on Twitter. Check out his other work here, like his look at the QB class of 2014, his analysis of the Josh Norman situation, the hidden game of Super Bowl 50, and Bill Belichick’s apparent hatred of Round 5 of the NFL Draft.

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