3-4 Run Defense: Part I

This is Part I in a series of posts I'm going to do in looking at 3-4 run defense. Today, we start by looking at game theory in the running game, run fits, and how to attack the Ace formation.

The two fundamental skills in football are blocking and tackling, as I have said before; the two fundamental musts for winning football are running the football and stopping the run. You have to be able to run the ball when you want to win games, and you have to be able to stop the opponent's running game.There is nothing more satisfying than watching your offense be able to run the ball at will on an opponent, knowing that they are helpless to stop you from exerting your will; conversely, there is nothing more frustrating than watching an opponent run all over you, knowing you are unable to stop them.

In the running game, you have eight possible gaps to attack. If you go with five offensive linemen and two tight ends, going from left to right, there are eight possible gaps you have to defend.

8 Gaps In Offensive Line

In an Ace set, which is 12 personnel, or 2 TEs and 1 TB, these eight gaps are clearly represented. You can run off the C-G gap, off the G-T gap, or off-tackle in the T-TE gap to either side, giving you eight possible gaps to run to. A defense which is gap-sound must be able to fill all eight gaps in the offensive line, or the run defense wll break down. As we all know, we're going to be running a 3-4 scheme this coming season under Tim DeRuyter. Let's look at how a 3-4 might align against an Ace set.

3-4 Defense vs. Ace Set

We have our OLBs aligned in 7 techniques, or NG head up in a 0 tech, and our DEs both in 3 techs. The Mike ILB is in an 11 tech, the Will is in a 20 tech, and both CBs are aligned off the LOS, ready to drop into zone coverage, or to come forward in run support. The FS is back deep, playing Cover 1, while the SS is up in the box, ready to help in run support or drop back into pass coverage.

How will we cover the 8 gaps?

3-4 Defense Run Fits Versus Ace Formation

The NG will rush the weak A-gap to his right side (since most teams are right-handed, we're naming the offense's right side the strongside of the formation), the Mike ILB will fill the strongside A-gap, the strongside DE will fill the B-gap, the SS will fill the C-gap, and the SOLB will force the run back inside by filling the D-gap. On the weakside, the WDE fills the B-gap, the Will ILB fast flows and fills the C-gap, and the WOLB fills the weak D-gap. Eight gaps, eight defensive players, one perfect run fit to fill all the gaps. This alignment also leaves you with three secondary players to cover two WRs, so if you're facing a stud game-changer at one WR position, you can bracket him in coverage with the FS and one CB. This alignment is gap sound against the running game while also giving you a good pass defense. 

There are only so many plays a team can run out of the Ace formation, and because of the trade of a fullback for a TE, there are really only two possible ballcarriers, the QB and TB. In theory, a WR can be motioned into the backfield to act as a sweep or option threat, but reality is that you won't see that often, if ever in games. The main plays you'll see our of an Ace set are Power, Counter, Zone (Inside or Outside), Zone Option, Stretch, and Speed Option. Notice that only two of those plays,the Zone Option and the Seepd Option, can really feature the QB as a running threat, so the defense only has to focus on the TB on run plays the vast majority of the time.

While the balanced nature of the Ace set seems to give you a lot of options because you can run plays to either side, the limitation of the set is that you have fewer passing option, so coming out in this set means you are going to run the ball about 75-80% of the time. By studying tendencies by down, and by looking at simple game thoery, you can deduce what most teams are going to run and when they are going to run. On 1st and 10, you have all running plays available to you, but wanting to get ahead of schedule means you're going to try for a long gainer, so Power, Zone Option, Zone, Stretch, and Speed Option are likely. On 2nd and 8-10 yards to go, you're going to to want to get back on schedule, so you'll go for similar big gainers, but not wanting a loss, will probably not drop Speed Option, Inside Zone, or Zone Option. On 3rd and 6-8 yards to go, you are behind schedule, so you'll probably be passing the ball, which means the defense has succeeded by shutting down your running game, and putting you behind schedule. If you are successful on 1st or 2nd down, and face a 3rd and 1-3 yards, you'll go with a short yardage play, like Power or Inside Zone. The defense probably won't see Counter until it has been hit with Power a few times, or if the offense thinks the LBs are keying the TB. Beacuse there is no true weakside in the Ace formation, you don't see Counter run very often, because it really isn't necessary.

Because the Ace set trades two WRs for two TEs, simplifying pass defense, and because there are only so many plays you can run out of the Ace set, stopping the Ace set with a 3-4 defense is actually relatively simple. As long as the defense studies game film, knows the offense's tendencies by down and distance, they will know what plays to expect when they see an Ace set, so it will be easier to shut down their running game.