Summary of References for our Defensive Strategy

Much has been written about the Eagles defenses of the past few years and speculation around how the new coaching staff will work to put a better product on the field going forward. This is not another post chiming in, but rather a synthesis of the references that have best helped me to digest the changes we can expect. First is a review of the defensive strategy highlights and then a breakdown position by position of how this strategy cascades into specific positional needs. This breakdown should be helpful when evaluating potential free agents or draftees.

While none of the content is original (all is fairly credited), when I found myself taking notes to pull all of the different nuggets of information out there together into one place, I decided to share in case others were in the same boat - hopefully this synthesis provides helpful to others as well.

Defensive Strategy

Our new defensive coordinator seems to favor the 4-3 under defense, judging from his days in Arizona:

"Everybody puts us in that 3-4 category, but what we are is an 'under front, a 4-3 'under' defense, "Davis explains. "The 'under' is almost a 3-4. As 3-4 [defenses] go, it's not really what we do here." (1)

"Davis has coached this scheme with the Giants and 49ers, but this is the first time in a while one of his defenses has used it as the base grouping. He has picked up pieces of different schemes from a bunch of different schools around the league and likes the flexibility of what he and the other defenses have discover in the 4-3 'under' formation." (1)

Assuming we do move to the 4-3 under (as seems to be the consensus), there are a few great summaries out there of how it works and what is needed since this is also the defense Pete Carroll runs in Seattle. Below are some of the articles I found most informative, and some primary excerpts from them (although I recommend reading each in full):

USC 4-3 Under Defense Blitz Plays - Pete Carroll (2):

"In principle we want to give our players a chance to know exactly what they have to defend. We also want to give them an attitude in which to do that. We want to be an attacking, aggressive football team. We don't want to sit and read the play like you often have to with "two-gap" principles of play. We want to attack into the gap at the snap, get off the ball to play on their side of the field and get after the quarterback." (2)

"The big problem with any "one-gap" approach however is that it allows a ball carrier to get into the secondary if one guy makes a mistake. No matter how aggressive the defense is there is a great amount of discipline that goes with this defense. You have to be very strict about your positioning and the placement of your players. You have to have the ability to maintain relative spacing between your players." (2)

"The front five players I mentioned are playing aggressive defense with their outside arms free. The only thing we can't allow to happen is for them to get hooked or reached by the defender." (2)

"If you have a million reads for your secondary you are crazy. They don't need that even at our level. All they need to know is their primary responsibility and then secondary. At the highest level in the NFL the pass game is as complex as you can imagine. However if a defender can play the post and the seam route then they can learn to play at that level. The thing that kills and breaks down a defense is a ball being thrown over the defender's head for a touchdown." (2)

Introduction to the 4-3 under (3):

"The defense that Pete Carroll now employs uses the basic tenets of the Monte Kiffin 4-3 Under defense and mixes in a variation originally pioneered by the legendary George Seifert in San Francisco. Seifert wanted to create mismatches against the opposing offensive line so he started using his weakside defensive end to rove around and rush the passer from a two-point stance (standing up position). This was the beginning of the "Elephant" position and one that Carroll uses today. We also see this position called the LEO, and in the Hawks' defense can rush standing up or in a three-point stance." (3)

"For the most part, each lineman and linebacker is responsible for one gap - this makes each player's responsibility fairly cut and dry and eliminates a lot of the reads and thinking from the game." (3)

"The 4-3 Under can be run with any combination of secondary assignments, the Cover-1, Cover-2, Cover-3, and even the Cover-4, and the Seahawks run different zone coverages at different times." (3)

General discussion of length and toughness:

"If new Eagles coach Chip Kelly adopts some of the strategies he was using at Oregon, the Eagles will begin coveting "longer" players. Kelly's NCAA teams were known for their speed and stamina but Oregon was also recruiting taller players across the board, particularly on defense where he made length a priority with a recent change in philosophy. Some people around the league believe the Eagles will begin seeking taller players on that side of the ball." (4)

"On Monday, Bill Davis used the tough, physical San Francisco 49ers defense as a benchmark for the kind of squad he wants to build". "I think you have to pick them that way," Davis said. "I think you have to do your research and pick players that have a tough mentality and tackle well." (5)

Positional Breakdown

Here's a view of the 4-3 under from the Seahawks front, courtesy of


DT (3-Technique):

  • The weakside defensive tackle, the 3-tech, must be your premiere interior pass rusher and have an explosive first step. His main job is to pressure the QB and stop the run in his weakside B gap (3)
  • In terms of size, I'd say that over 6'2 and around 300 pounds would be the standard for the 3-tech. He must be strong and big enough to hold up against the run but also quick and agile enough to get off his block and get to the quarterback. This is one of the hardest players in the NFL to find (6)
  • He is going to get a lot of one on one blocks as it is hard to double team him because of where he lines up (2)

NT (1-Technique), aka strongside DT:

  • The strongside defensive tackle can be short and squat but must be able to take on a double team consistently (3)
  • At Nose Tackle you have to find a player who likes to mix it up. We want a big guy in there who likes to get down and dirty. He is going to get doubled a lot on the run and pass and is going to get down blocked a lot. He has to be a tough player. This guy can be a short and stubby type of player (6)

DE (5-Techique):

  • The 5-tech defensive end can be a bigger guy and must be great against the run (3)
  • The defensive end to the tight end side needs to be a defensive player that can play the run. He does not have to be a big time pass rusher (6)
  • For the most part, the way that Carroll envisions it, Bryant, or a bigger run stuffing defensive linemen, sits back and takes care of two gaps, primarily concerned about stopping the run. In obvious passing downs though, his goal is to push the pocket and create a vice for the quarterback as best as he can (6)
  • The 5-tech player in this defense can be bigger, significantly bigger, than a normal 4-3 defensive end. Red Bryant is 6'4, 323 and most probably the biggest dude at that position in the NFL. But Bryant has a pretty rare combination of speed and size so you're not going to find many players in his mold (6)
  • Meanwhile, the other defensive end (to the strong side) won't get as many advantageous pass-rushing opportunities and needs to be able to play the run well (7)

The "Predator", aka the "Elephant", aka the "LEO":

  • The LEO can be a little bit smaller than a normal DE and Pete Carroll tends to like a more athletic and versatile body type for his Elephant position; a guy that can speed rush the QB but also react quick enough to control his gap. Must also be able to drop back into coverage occasionally in zone blitz situations (3)
  • The best pass rusher on the team is usually the defensive end to the open side of the field. That puts him on the quarterback's blind side and makes him a C gap player in this defense. We often align him wider than this in order to give him a better angle of attack and allow him to play in space. We align him a yard outside of the offensive tackle most of the time. He has to play C gap run support but at the same time he is rushing the passer like it is third and ten. He has to be able to close down however if the tackle blocks down on him. (He) has to be one of your best football players. Size does not matter as much. We want an athletic player who can move around (6)
  • The other linebacker, which he calls the "predator," lines up on the weakside and is almost exclusively a pass rusher. Davis explained that these guys are typically DEs by trade (8)
  • And then there's the pass-rush specialist on the other side. This is the player Davis referred to as the "Predator." For the Cardinals, that spot was occupied by Bertrand Berry and Travis LaBoy. Per PFF, Berry rushed the passer 94 percent of the time and dropped back just 6 percent. For LaBoy, the exact same percentages applied (7)


  • The SAM linebacker needs to be athletic and rangy; great against the run but able to run with tight ends and running backs in pass coverage (3)
  • The Sam linebacker has to be a good containment player. He has to be big and strong enough to play on the edge of the tight end. He has to be able to run in pass coverage also (2)
  • According to Pro Football Focus, he rushed the QB about 70 percent of the time and dropped back about 30 percent on passing downs (7)


  • The WILL linebacker is going to get a lot of tackles and in Pete's system is typically a faster, smaller linebacker with range (3)
  • He is basically a protected player in this alignment and should make a lot of tackles (2)
  • The Will linebacker can be a smaller player. He is generally protected in the defensive schemes and will not see as many blocks. All you want him to do most plays is flow and chase the football. We want our fastest linebacker at this position (2)
  • The way the defense is set up, he has a nice protective shield to keep potential blockers at bay. "what we've done with Karlos is put him behind a three-technique, so basically - we call these anchor points - he's got a wall in front of him," Davis said. "So he can run and use his athleticism. The center can't get him because the nose is on him. The guard can't get him because the end is on him. And the tackle can't get him because the predator is on him. So this is your athlete that can run, go cover ground and make plays (1)


  • The MIKE linebacker needs to be the field general; very instinctual and savvy. He needs to be quick enough to drop back down the middle third of the field in pass coverage in the Tampa-2 coverage (3)
  • The Mike linebacker is a traditional middle linebacker. He is instinctive and makes a lot of calls for the defense. He may be the guy with the most experience or the best feel for the game (2)
  • That's my thumper, more of a thick guy (1)


  • The free safety is a guy that's going to move around a lot and be very instinctual as well. He's going to come up to the line a lot and will get a lot of tackles (3)
  • The Free Safety is the force player to the open side or weak side of the ball. He works off the defensive end's play. The Defensive End works for leverage and force. The Free Safety works off of the Defensive End and fills where he is needed on run plays for example (2)
  • The Free Safety is another player who makes a lot of tackles for us. He has to have good instincts. He is what we call a natural player. You don't have to coach this player too much. He has to have a feel for the everything and understand the big picture (2)


  • The strong safety has to be good against the run but like the free safety, will move around a lot and have to defend against the deep pass a lot. He will need to be fast and have some ball skills (3)
  • If we are playing Cover 3 behind him the Strong Safety is going to have the middle of the secondary behind him but also fills off the linebacker's side as needed depending upon the play. If the Sam linebacker does get hooked for example the Strong Safety will then have to come up and make the play (2)


  • The cornerbacks need to be physical and long. They will get involved in run defense a lot so they must be good tacklers. They are protected over the top a lot of the time so typically they're not all-world defenders but need to be pretty fast. You see Pete running with solid, physical and tall corners but in his tenure at USC we didn't see any all-world prospects come into the NFL (3)


  1. Edlholm E. Chiefs Planet. [Online].; 2009. Available from:
  2. Carroll P. Trojan Football Analysis. [Online].; 2010. Available from:
  3. Kelly D. SB Nation: Field Gulls. [Online].; 2011. Available from:
  4. Pompei D. National Football Post. [Online].; 2013. Available from:
  5. Seridan P. [Online].; 2013. Available from:
  6. Kelly D. SB Nation: Field Gulls. [Online].; 2011. Available from:
  7. Kapadia S. Birds 24/7. [Online].; 2013. Available from:
  8. Bleeding Green Nation. SB Nation: Bleeding Green Nation. [Online].; 2013. Available from:
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