X's and O's Mailbag: Def. Schemes - Part One

In our new weekly series, GoBlueWolverine tackles your questions about anything football. Josh Turel and Victors Club Message Board poster "CoachBt" break down the onfield X's and O's. In part one of this edition, "CoachBt" explains the differences between the 3-4, the 4-3, and the 4-2-5.

This week's question was submitted by Victors Club Message Board poster. "rwburns819."

Question: What are the primary differences between a 3-4 defense and what we may see from Ron English's 4-2-5 front. What are the strengths and how would an offense attack each of the weak points. Looking at our personnel, which defense gets our 11 best players on the field?

For a detailed description of Gaps & Techniques, be sure to check out GoBlueWolverine's feature on the topic from last March.


Starting with the basics of each scheme, the 4-3 uses four linemen and three linebackers, while a 3-4 uses the opposite. It is the personnel however, that is the biggest difference. A 3-4 uses basically three defensive tackles as the linemen. The 3-4 is also called a two gap front because each defensive lineman is responsible for two gaps at the line of scrimmage. The nose tackle is responsible for both A gaps (gap between the center and guard to each side), and each defensive tackle is responsible for both the B and C gap to his side. This takes defensive linemen whose primary skill set is great strength. Most offenses will double or combination block against the 3-4 front. Their job is tie up the line of scrimmage and keep linemen off the linebackers. If offensive linemen are able to get to next level and get a body on the linebackers, especially the inside linebackers, the 3-4 is not going to be very effective.

The 4-3 defense, on the other hand has D linemen, responsible for single gaps. Those gaps generally change depending on which way the defense stems or shifts the front. They can stem to either the formation strength or to the wide side of the field. When a 4-3 stems, it becomes very similar to the 3-4 when it off sets to strong side. In a base 4-3, one defensive lineman, usually called a 1-technique tackle is responsible for the A gap to one side or the other. The other defensive tackle is usually responsible for B gap to the other side and is called a 3 tech DT. Many 4-3's will flip or switch defensive ends to one side or other. One defensive end will be a strong side end and will line up against the strength of formation. The other defensive end is sometimes called a rush defensive end, and goes opposite of the strong side defensive end. Many teams will always put the strong side end to the tight end side and his primary function is to keep the tight end off the linebackers and then play either the off tackle run or contain against stretch or outside zone play. The rush defensive end and 3 tech DT are usually the "stars" of the 4-3 front.

The biggest difference between the 3-4 and 4-3 is the linebacker play. Besides the obvious two inside linebackers in the 3-4 compared to one in 4-3, their gap responsibilities are greatly different. Middle linebackers in a 4-3 are responsible for A and B gaps to both sides of ball. In the 3-4, linebackers play what is called force and scrape. The inside linebacker to ball side will take on blockers. The linebacker to the other side is the scrape linebacker and must make tackles. Outside linebacker play is similar in both defenses. Weakside linebackers basically have flat responsibilities and are basically strong safeties in many situations. Speed and quickness are very important skills for him. The strong side linebacker usually goes to TE side. He is primarily a run first and pass 2nd player. In the 3-4, many times the strong side linebacker will actually play on the line of scrimmage and be responsible for keeping the tight end from attacking the free safety.

As for defensive back play, there is very little difference. It all depends on your system and philosophy. Are you playing zone blitz? Are you rolling to the wide side or to the formation? Both defenses can play 3-under or 3-deep coverage. Both can play 2-deep or any other combination you want. If the 3-4 has one advantage it is easier to adjust out of it because you have an extra linebacker in the game. You also have more flexibility in blitz packages and stunts.

With the 4-2-5, you have an extra defensive back, so in theory you should be more athletic and faster. However, this advantage comes with the caveat that you have less size in the game and could be vulnerable to power running game. That is unless one safety can play at the line of scrimmage and take on fullbacks and guards. This defense could experience trouble against teams like Wisconsin or Minnesota if the personnel isn't optimal.

On the positive side, it gives you lots of flexibility because of the extra defensive back and it is a very good defense against spread teams and in certain down and distance situations. It makes an excellent nickel package.

For Michigan, utilizing the 3-4 as a base defense is probably not the best course of action. The Wolverines defensive line could very well be strength of the team. Playing the 3-4 would take one of the best players off field unnecessarily. In my opinion I think playing a combination of 4-3 and 4-2-5 would be great fit for Michigan's personnel in most situations. I could see them playing a 3-4 or some sort of variation in prevent situations as well.

In part two, GoBlueWolverine's Josh Turel will go into more detail about the pros and cons of the 4-2-5.

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