Updated: Sep 24, 2019
In the LEVELS and SEAMS blog I gave a brief introduction to how the offense looks at the structure of a basic Cover 3 defense. There are various methods that a defense can structure itself to establish these areas. They are influenced by coaching philosophy, players experience, defensive team speed, down and distance, and what they evaluated when scouting their opponents.
SAFETY - the depth and positioning of the safety can give the offense a lot of information about the coverage that they might get at the snap of the ball. A deep safety in the midle of the field is useless going to predict a odd deep zone coverage scheme like Cover 3 or man coverage scheme like Cover 1. If he cheats to one of the hashes we would move our eyes to another defender to see if they are more likely to be adjusting for an even deep zone coverage like Cover 4 or man under cover 2. Obviously this would create 5 seams at the third level and more defenders to protect against the deep passs.
LINEBACKERS - After a LB gets his pass read he will look to cross over and drop into his zone. There are many schools of thought about how far he drops. Talking to a defensive coach he might tell him to get to a depth of 12 yards to establish Level 1 but another coach might tell him to drop as fast as he can until the QB stops his drop. Typically a 3 step drop by the QB will initiate a quick throw to a shorter route and a 7 step drop would indictate the likelihood of a deep pass.
HALFBACKS (HB) AND CORNERS(CB) - Defenses will alternate who they use to be the underneath coverage defender based on the prediction of what the offense might call. If they want to support the likelihood of a run play they are more likely to have the HB play low but if the offense has been throwing vertically down the hash marks or short out by the sidelines they might have the HB drop deep and ask the CB to be the underneath coverage. When the HB is involved in the underneath coverage, the Defensive Coordinator might have the philosophy of protecting against that vertical throw up the hashes (or SEAM B) by asking the the HB to hold that Seam until a receiver crosses his face and forcing him to step up and set Level 1.
DEFENSIVE LINEMEN (DL) - When they get involved in playing zone coverage the game can get more complicated for the offense. "Popping" or "Peeling" a DL to add another underneath defender or exchange roles for a blitzing LB can add an element of surprise to the QB post snap. A good strategy when the offense has been using crossing patterns or midline hook plays.
On the offense we should be able to find the holes in the defenses' coverage scheme. When the receivers run crisp routes, the OL controls the rush and the QB gets a clean read and anticipates the throw, the offense will be able to move the ball down the field.
FYI - a big adjustment by defenses has been the addition of LEVEL 0. When they get the offense into long distance situations they will allow the underneath pass in this LEVEL 0 and ask the defenders to rally downhill to stop the ball carrier short of the first down sticks.