The 3-3 Stack is a three-man front that has three linebackers lined up directly behind the defensive linemen. Thus, the name “stack”. It is also called 30 Stack, Stack, or the 3-3-5 defense. The defensive linemen are aligned directly over the two tackles and the center.
Differing from two-gap 3-4 schemes, the Stack is a one gap defense. Defensive linemen will slant into gaps and the linebackers will fill the complimentary gap that the defensive line has vacated. There are more stunts and twists in the 3-3 Stack than you usually see in the 3-4. That simplifies the assignments for the defense while giving the offense varied post-snap looks out of the same pre-snap look and alignment.
Joe Lee Dunn came up with the 3-3 Stack while he was at Memphis in 199 and it was later adapted by Charlie Strong to help combat spread offenses. The 3-3 Stack requires linemen that can control their gaps and pass rush so that the linebackers can stay free to fit and make plays. The alignments creates confusion with different linebackers blitzing and different types of line stunts from play-to-play.
How to Identify the 3-3 Stack
The 3-3 Stack has:
- Three defensive linemen aligned head up over both tackles and the center
- Directly behind those three defensive linemen are three linebackers
Strengths of Stack
Differing gaps and a variety of post-snap looks
The biggest advantage of the 3-3 Stack is that the assignments and extra rusher changes from play-to-play. The onus is on the defensive coordinator to turn the 3-3 look into more generic fronts via blitzes and slants post-snap. To do that, they have to call the slants and pressure looks based on the formation and offensive tendencies. The Stack can tempt offenses to run a certain way and catch them with slants and extra defenders that direction with good defensive play calls. That also makes it harder for offensive linemen to understand their assignments and get up to the second level when there is post-snap movement from both the defensive line and linebackers.
More athletes on the field to stop spread and passing attacks
The 3-3 Stack replaces one defensive lineman with a defensive back. That immediately gives the defense more athleticism and speed on the field to combat spread teams or teams that throw the ball.
Weaknesses of Stack
Defensive linemen need demand blocks
The nose is especially important in the 3-3 Stack and if they can demand a double team or two-gap, it makes the life of the linebackers much easier. The defense is replacing a lineman with a defensive back, so they will naturally be smaller and have a tougher time defending the run. In return, they have more speed to stop the pass. That makes it even more important for the defensive linemen to demand blocks and keep the second level clean.
Running the ball
Ultimately, the 3-3 Stack has a six-man box. That leaves them susceptible to power run game and inside runs. The stacked linebackers over the offensive tackles can be hard to get to since they’re protected by the 4-technique in front of them, but adding additional players to the box with a tight end or fullback can mitigate that issue on inside runs.
The 3-3 Stack utilizes a six-man box with an extra defensive back on the field to help combat spread passing teams. It leaves the defense vulnerable in run defense, but can create confusion and exotic looks for the offense to handle.