Defensive football is really a structure of triangles. Whether it is the alignment and responsibilities of the front seven or how zone coverage unfolds when a pass play has to be covered, the basic structure of all defenses is a triangle.
A cover-two corner in the flat with an outside linebacker in the curl and a safety behind both of them splitting the width between the backer and corner set up a triangle. Two deep safeties split the field in half and a Tampa-two middle linebacker dropping deep in the middle sets up another triangle. A deep free safety in the middle of the field and two inside linebackers in curl zones is another example of a triangle.
The job of an offense is to destroy the structure of these triangles and move the ball.
When you hear people say that "it all starts up front," nothing could be more accurate especially in the middle triangle on defense. There are two structures that define the middle triangle on defense. If a team is in a 4-3 defense, its middle triangle consists of the two defensive tackles and the middle linebacker. If the team is in a 3-4 defense, the middle triangle is an invert of the 4-3 with a nose tackle and two inside linebackers.
Whether it is the inside running game, the off-tackle running game, the outside running game, or the passing game, if this critical triangle isn't sound and sturdy the entire integrity of the defense is destroyed. There are many NFL insiders who believe the demise of the Chicago Bears this year was really based on the breakdown of their middle triangle.
Last year when Tommie Harris and Tank Johnson were the defensive tackles and Brian Urlacher capped off the triangle of their 4-3 model, the Bears were unstoppable on defense. If the run came inside, they stuffed it. If the run went outside, the whole triangle would move to the ball. If the opponent passed the tackles would collapse, the pocket and Urlacher dropped. The Chicago middle triangle is far from what it was a year ago. The Bears let their depth go in free agency (Alphonso Boone, Ian Scott), Tank Johnson was dismissed from the team and this year's backups (Anthony Adams, Antonio Garay) were injured and all of a sudden the Bears struggled to stop the run.
I talk with a number of NFL centers every week and we discuss the best middle triangles in the league. As you might expect, it's not so critical that a team uses a 4-3 triangle over a 3-4 triangle but rather that they have the right kind of players for the structure and they are effective. Through 15 weeks, the best two middle triangles in the NFL represent the two different schemes. Minnesota is the top 4-3 team and the Ravens are tops among the 3-4 teams. Next up for the 3-4 teams is Pittsburgh while second-best 4-3 team was Jacksonville before it lost Marcus Stroud and middle linebacker Mike Peterson.
Most teams surrender the idea of even running on either the Viking or Raven triangle because they combine power and speed to destroy the blocking combinations. The Vikings' Pat Williams is a load inside and can't be moved. Kevin Williams has power and incredible quickness to penetrate. As one center said to me, "It's impossible to even get a clean shot on E.J. Henderson with the Williams boys in front of him."
As for the Ravens they start with a fire-plug nose tackle, Kelly Gregg, who can split a double team, slant into a gap and just be downright disruptive inside. Bart Scott and Ray Lewis know that one of them is free when Gregg does his job and their production proves it.
There are a few other teams like Dallas, New England and Green Bay that have excellent middle triangles, and I would be remiss if I did not mention them. As one NFC center said to me, "We try our best to split that middle triangle and not let it work as a unit but the teams you mentioned are close to impossible to divide."
When you watch the games this weekend, discipline yourself to focus on the middle triangle before the ball is snapped and watch the threesome work together to dominate the line of scrimmage.