This article goes further in depth about over/under defense then a previous one vs two gap defense. Even though that article is a 101, it covers more about gaps.
Back in the day, over/under defense was the old 4-3 front. If the front was over, the 3 Tech would line up to the Y. If it was an under defense, the 3 Tech was lined up away from the Y.
Some Okie (traditional 3-4) fronts have turned into Okie Over and Okie Under to accommodate the 1 gap pressure schemes. This means the N is now shading to and from the TE.
This defense makes the count in pass protection tricky. When a QB sees a 4-3 front, it’s really easy to count how many guys are on each side of the ball, but also helps the OL with declaring the MLB (MIKE). This helps the OL start to sort out who’s got who.
Same thing in the run game. However, when a defense lines up odd, the QB has to wonder, “are they now in a 1 gap or are they gonna play it straight up and 2 gap us?” The running back is looking at this, too. Experienced QB’s will help teach their backs how to read this.
The goal of over/under defense it to make the accounting process for the QB difficult on 2 levels.
1) he can’t accurately count how many guys are on each side of the ball and
2) there can be confusion between the C and QB on who the Mike is, leading to protection miscommunications between the OL and RB.
Okie Under can put new QB’s out of their depth in trying to read what these defenses are doing.
The best team to use the Okie Under to perfection was Denver’s defense in 2015. They rarely blitzed, it was all 3 and 4 man rushes, but it was the speed of DeMarcus Ware and Von Miller that didn’t give QB’s time to breathe, nor did OL’s know who to block.
The same odd man formation works in a 4-3, as well. This is why rookie O-Lines, especially with new tackles and slow processing QB’s can get slammed. To counter this, I think is why we’re seeing more RPO’s.
Jacksonville will be seeing 4-3 defenses this season who will shade their N away from the TE like above. The issue Blake Bortles and Nate Hackett face this season is the starting TE is new.
They practice against a 4-3, so 43 over/under defense won’t give them fits. Plus, this season the OL are a veteran bunch
Where’s the pressure coming from above? Will it be a one or two gap and who is Mike? While the 4-3 Over looks like an easy read, it isn’t because any of the three backs can be Mike. A QB needs experience to know who is Mike, what look the defense is giving and also figuring out what the safeties are actually doing. This is why the longer they play, the better they get at the mental side of the position.