While most high school teams use a 50 defensive scheme, the 43 defense remains at the top on most college and professional teams.
The 43 defense is one of the most used defensive schemes and is named for the configuration of defensive linemen and linebackers. You have four (4) defensive linemen and three (3) linebackers, hence the name 43. If you had three (3) defensive linemen and four (4) linebackers, you would have the 34 defense, which you can read about elsewhere.
It’s simple to understand and easy to implement. Take a look at the diagram below.
The four Xs are your four defensive linemen. The three LBs are your linebackers. LBs are usually named for the position they play. There are 3 main positions; middle LB, weak side LB, and strong side LB. Weak, strong, and middle are also referred to as Will, Mike, and Sam. So a Sam blitz, is when the strong side LB moves up into a gap and blitzes. The strong side is the side where the TE is lined up on.
The CBs are the cornerbacks and the Ss are the safeties. Every player has a specific role based on how the offense lines up and what the defense is doing. The above configuration shows a Cover 2 type of defense. What is Cover 2? You have two safeties covering the deep routes. When you bring a safety up to blitz, or cover a WR man to man, you will end up with Cover 1.
The CBs play a short zone in the purple zone as above. They do not follow the receivers if they go too deep or too far to the middle. They stay put in their zones.
The safeties cover any WRs that go deep and downfield past the zone that is covered by the CBs.
The LBs are crucial. They cover the RBs, the TE and anyone else that comes at them. If it is a running play, they go up and make the tackles. If the TE goes out on a pattern, they cover him as long as he is in their zone. Once he goes too deep or too far to the sidelines, they can leave him. Some defenses will chose to cover the TE man with a LB. Find out what your coach wants to do.
The defensive line attacks the QB. There responsibility is to go after the QB and tackle the RBs on run plays. Very simple.
What if the instead of a TE, they use an extra WR? How would you adjust?
Basically, you don’t want to change anything. The CB on that side still covers his zone. That may mean that he is covering two WRs, and that is ok. Once the ball is snapped, one WR may go deep, while the other goes outside. If one of the WR takes an inside route or goes over the middle, then the LB picks him up. If he takes a short outside route, the CB takes him. This means that the S on that side has to be more aware and more intelligent.
Instead of putting in a 3rd WR, they may motion the 4 RB or the 2 RB to a side in order to get the defense to react or confuse the defense. Just treat the motioned RB as if he were a third WR as explained above.
What if they bring in 4 WRs? Then what can you do?
You still don’t change anything. A lot of backyard players and playground players who are used to covering all WRs man to man may not understand this concept, but it is simple. Only one CB covers the short zone area on that side (in the purple oval). In this scenario, the LBs can play further away from the ball and closer to the WRs. With only one RB to worry about, they don’t have to play as close to the middle of the field.
Blitzing from this type of defense can be done from many different positions. You can blitz a S, you can blitz one of the CBs, and you can always blitz an LB. Adjustments can be made for the player that is blitzing. If a CB is blitzing, the S on that side can cheat up a little. If the S is blitzing the other S can cheat to the center more.
Of course, there are tons of adjustments and some very complicated schemes in the 43 defense. This is a basic overview and hopefully will get you started in your defensive football knowledge. Feel free to discuss this and make suggestions in our forums.