Under

The Under set in the 3-4 formation is a shifted front built to take away the strong side run game while keeping a full menu of pressure and coverage calls. Instead of the balanced alignment you get in 3-4 Odd, the Under shifts the defensive line toward the weak side. The NT shades the center toward the weak side A gap, the RLE and RRE reset into tighter techniques, and the strong side outside linebacker walks up on the line over the tight end. The result is a Base 5-2 () look with five players on the line of scrimmage and two stacked inside linebackers. This front clogs interior gaps, forces runs to bounce outside into your edge defenders, and gives you a true 4-man rush feel with 3-4 flexibility behind it.

What separates Under from the other 3-4 sets is how much it disguises. The same pre-snap shell can roll into Cover 1 Robber Press, Cover 3 Match, Tampa 2, Cover 4 Quarters, or Cover 6. It can also show pressure like Pinch Buck 0, Saw Blitz 1, and Dbl Safety Blitz. Because the stand-up OLB on the strong side can rush, drop into the flat, or carry the tight end, offenses cannot key a single defender to read the call. That forces opponents to make their reads after the snap, when your coverage has already rotated.

Personnel-wise, the Base 5-2 () package keeps four linebackers on the field. That is ideal against 12 and 21 personnel, heavy I-form looks, and tight end-centric passing attacks. You get linebackers who can match up physically with tight ends and fullbacks in man coverage, and your corners are free to press outside receivers. The tradeoff is speed in space: against empty or 4-wide spread sets, your linebackers can be isolated on shifty slot receivers. Smart offenses will motion to create those mismatches.