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Cover 3 zone is a MOFC (middle-of-field-closed or single-high safety look) that has 3 deep defenders on the field. The primary advantage of a cover 3 defense is its ability to put an extra defender in the box to stop the run.
The basic alignment for cover 3 puts a cornerback in each deep third with the free safety in the middle third. The strong safety begins the play either in the box or aligned over the top of the slot receiver and is responsible for one flat while the opposite linebacker is responsible for the other flat. The remaining two linebackers are “hole” defenders and cover the hole in the middle of the field in a defensive assignment called a hook zone.
The primary goal of a cover 3 defense is to protect downfield and force underneath passes, then rally and tackle to limit the yards after the catch. It is vital that players in a cover 3 defense be good tacklers.
There are two different flavors of basic cover 3: cover 3 sky and cover 3 press/buzz. The major difference between these two is that in cover 3 sky the outside cornerbacks will be aligned around 7 yards off the receivers whereas in cover 3 press/buzz they will be aligned on the receiver and will press them at the line.
What is the weakness of Cover 3?
The primary weaknesses in cover 3 are the seams (the area between the deep zones) and the flats (the area near the line of scrimmage on each side of the field.) An NFL football field is 53 yards wide and a cover 3 defense tasks three defensive backs to cover that entire width downfield while relying on 3 linebackers and a safety to cover the underneath portion of the field. The problem for defenses is that linebackers aren’t as athletic as defensive backs and can often struggle to cover all the way to the sidelines. A linebacker’s natural instinct will be to start cheating outside which can then open up quick passes exploiting the seam.
Offenses will often run a flood concept against cover 3 where an outside receiver runs a vertical route to run off the deep corner, a 2nd receiver runs an out rout 10-15 yards downfield, and a running back runs to the flat. This puts the flat defender in an impossible situation as he is now responsible for covering 2 players that are 10-15 yards apart.
In this situation, a linebacker in a hook zone must quickly recognize what the offense is doing and help the flat defender or the offense will pick them apart.
Another way an offense can attack a cover 3 defense is by simply running 4 receivers down the field vertically. Four receivers deep vs. 3 defensive backs deep is not an advantageous situation for the defense. So how can a defense counter this?
Cover 3 Match
Cover 3 match is a pattern-matching coverage check that defenses can call to slow down a vertical passing attack. The concept is pretty simple and has 3 basic rules:
- The cornerback who is responsible for the outside third of the field will convert to man coverage if the outside receiver runs a vertical route
- The flat defender will convert to man coverage if the #2 receiver (slot WR or TE) runs a vertical route
- If both receivers on a side of the field run vertical routes the LB in the middle of the field on that side will cover any other route that comes to the vacated side of the field
Cover 3 match is basically a cover 3 defense unless 2 receivers go vertical on the same side of the field, and then it converts to man coverage with a deep safety to help over the top.
Cover 3 Mable
Cover 3 match works when the field is balanced (the same number of receivers on each side), but what about when the offense isn’t in a balanced set? In that case, the defense will check to a similar coverage called Cover 3 Mable. Here are the rules for this adjustment:
- The cornerback on the single receiver side converts to man coverage no matter what route the receiver runs
- The linebacker on the single receiver side converts to man coverage on the running back
- The corner on the 3 receiver side will convert to man coverage if the outside receiver runs a vertical route
- The safety on the overload side (SS in the diagram) will convert to man if the slot receiver runs a vertical route. If not he will play a deep zone.
- The safety on the single receiver side (FS in the diagram) will convert to man if the tight end runs a vertical route
- Regardless of route combinations, the remaining flat defender and hole defender will drop into zone coverage
I’m going to stop talking about special cases at this point because it can get extremely complicated very fast, but these are the most basic coverage checks that you will see out of cover 3. I do, however, want to show one more cover 3 adjustment that attempts to disguise the defense.
Cover 3 Cloud
When a defense comes out in a single high safety look it is a dead giveaway that the coverage is either cover 1 man or cover 3 zone. It is in the defense’s best interest to mask their coverage before the snap so the quarterback doesn’t know what is coming. They will sometimes do this by calling Cover 3 Cloud. Cover 3 Cloud has similar responsibilities to a normal cover 3 zone but the defenders will align in a MOFO/split safety look before the snap with the cornerbacks pressed up on the receivers.
This looks like a Cover 2 Man or Cover 2 Zone. But at the snap of the ball, the defense rolls into a cover 3 look with the cornerback on the side of the free safety (RC on the diagram) bailing into a deep third, the free safety rolling to the middle third, and the strong safety rolling to the other outside third. In this deployment, the remaining cornerback (LC) becomes the flat defender and the linebackers are unaffected by this roll technique.