Cover 3 is a zone defense with 4 underneath players, and 3 deep players. A defense like this allows you to distribute almost equal amount of players to the deep part of the field and the underneath coverage on the field.
Cover 3 is extremely common at all levels of football, and it's one of the coverages that many championship-winning coaches, like Nick Saban and Pete Carroll, have built a large part of their playbooks around.
In this article we'll be going in-depth on how the Cover 3 defense works, its strengths and weaknesses, and some other versions that a defensive coordinator may decide to use against an opponent offense. The scheme can help take away the threat of a big gain, but just like anything else, it has its own weaknesses.
How does Cover 3 work?
Basic cover 3 defense is a 4 under, 3 deep zone coverage. This means that there are three deep defenders, including a free safety in zone coverage in the deep middle, and two cornerbacks guarding three equally sized deep zone areas of the field to take away any vertical routes, break on any deep ball thrown in their direction, and eliminate the threat of any deep pass.
Deep Coverage Responsibilities
Traditionally there is no press coverage in cover 3. Instead, the corners "bail" with a safety to divide the deep part of the field into thirds, or backpedal to get enough depth to take away any deep routes. 3 linebackers and the strong safety rolling down in are the 4 underneath defenders.
When installing and practicing this defensive scheme with their players, most coaches use the hash marks as a landmark to divide coverage responsibilities between the deep coverage defenders.
In this example, the cornerback is responsible for the outside third of the coverage, which is measured from the sideline to the hash marks. In the middle of the field between the hashes is the deep middle zone defender's responsibility, and then outside the hash to the opposite sideline designates the opposite deep third.
Coaches tell their defensive backs to stay "deeper than the deepest" and their first responsibility is to stay on top of the vertical route that threatens them deep, even if there is a second route developing that may come open underneath.
Underneath Zone Defenders
In traditional cover 3, there are four underneath zones that need to be accounted for.
These zones are known as the Hook, Curl, and Flat zones, and they are located on both the strong side and weak side of the offensive formation.
The underneath responsibilities go from "Hook-to-Curl" and "Curl-to-Flat" so that the defense takes away the middle and deep parts of the field first, ideally forcing the quarterback to check the ball down underneath or in the flats where the defense can rally and make a tackle.
See the diagram below for an example of how these zones are designated on the field. It's important to remember that many defensive coaches have slightly different definitions or landmarks they use to teach these zones, so this is only meant as a generic example.
Why do defenses use Cover 3?
The purpose of Cover 3, is to add an additional defensive back to the deeper part of the field. In cover 2 there are 2 deep safeties, cover 3 adds a third defensive back to the deeper part of the field, with a deep corner to both sides of the field.
It also allows the defense to add an extra safety down closer to the line of scrimmage to help stop the opponent run game. If you're watching a game and you hear the announcer suggest putting an 8th man in the box to stop the run, playing a cover 3 defense is one way to do that.
Football strategy has a lot to do with numbers, and if you can get more numbers in a certain area of the field than your opponent, your chances of success go way up. If you have more defenders to play the run game than the offense has blockers, you're going to have a good chance to stop whatever they try to do running the football.
What are the strengths of Cover 3?
Cover 3 provides more of a balanced attack in coverage towards deep threats and intermediate routes. The 4 underneath players and 3 deep players are more balanced compared to a cover 2, where there are only 2 deep safeties and 5 underneath players.
Cover 3 provides a balance attack for an opponent that has a balanced run and pass attack. Through the course of a game you will be able to play defense against both the pass and the run.
This is a big reason why the cover 3 defense is extremely popular at the high school and college level, where the rules are different than the NFL level, and the run game traditionally has been more dominant.
Weaknesses of Cover 3?
The weak spots in cover 3 are the flats. Corners are bailing to the deep third traditionally which allows wide receivers to run a hitch, and out, or an arrow into the flat for positive yardage. Offenses may be able to “nickel and dime” you up the field completing short passes of 5-8 yards for a good percentage.
Defending the Seams
A lot of offensive coordinators love the four verticals concept against a cover 3 because it gets 4 players going on vertical routes against three deep defenders, and also presents some problems for a defense who wants to take away the seam route and hit that pass at the intermediate level.
The seam route is designed to attack that area near the hash marks, right in the area where the deep defenders on both sides could easily assume that the other would be responsible for the vertical route.
The other issue is a personnel matchup.
If the offense is running the "four verts" concept, it likely means that a tight end or a slot receiver is trying to go deep and beat a rolled down safety who also has some run defense responsibility.
This is a challenging assignment for a lot of players, and even though defensive coordinators have come up with some clever answers, it ultimately comes down to the talent level of the players you have at your disposal.
We will go over some answers for this later on in this article.
Stopping the Run
Against the run, cover 3 also struggles on the perimeter. Teams trying to get to your edge can find success as a corner is bailing to the deep third and a safety is coming down to the flat. Getting a blocker on your safety and your corner bailing creates a weak spot on the edge of the defense.
If the outside linebacker is playing too tight to the offensive formation, it's very easy to get out leveraged and provide a receiver to seal him inside for the perimeter run. Conversely, it's also very easy for that guy to play too wide over the slot receiver or tight end lined up inside, and create a lot of space for the run (or throw) inside of him.
This is why these players on defense have to be some of the most athletic guys on the field, because offensive coaches spend a lot of time figuring out how to make them wrong and get them out of position. If you're going to play a lot of cover 3, those guys have to be able to play well in space.
Cover 3 Rules
Left Cornerback - Deep Outside Third
Right Cornerback - Deep Outside Third
Strong Safety - Curl Flat
Free Safety - Deep Third in the Middle of the Field
Sam Linebacker - Hook/Curl
Mike Linebacker - Hook/Curl
Will Linebacker - Curl Flat
Cover 3 Variations
Now lets take a look at some popular variations of the Cover 3 defense and how a defensive coach can give their opponent a different look while presenting similar coverage calls.
Flip Your Safeties
This is called many things in different programs, but a great variation to cover 3 is just flip the jobs of the safeties. Have your Free safety roll down to the weak flat, and have your strong safety stay high in the deep third. Your strong outside linebacker will take the strong curl flat, and the Mike and Will linebackers will take the hook/curl zone.
Cover 3 Fire Zone Defense
If you’d like to add a 4th rusher, cover 3’s balanced attack gives you that option. It will put more stress on the non blitzing linebacker that is covering the hook/curl zone, but in this event, you are hoping your pressure gets there before that becomes a problem for him.
This is commonly referred to as a fire zone defense.
In a standard cover 3 defense, you're assumed to be sending at least four defenders after the quarterback. If you're lining up in a 4-3 defense like in this diagram, you can just let your four defensive linemen rush the passer and drop everyone else into coverage.
On the other hand, if you're sending more than that (five defenders or more) while playing zone behind it, that has a separate designation as a fire zone defense.
If you're playing with four defensive linemen, it's also very common to drop them off into one of the short underneath zones when you're blitzing some of your underneath defenders. This is a great curveball to throw at opposing quarterbacks.
When the QB sees the pre snap picture of multiple defenders creeping up to the same side, they may think that you are playing man coverage behind the pressure, and end up throwing the ball to a big defensive lineman.
This can be extremely confusing for the offensive line as well, and defenses can create a lot of sacks just by having the defensive end drop into underneath coverage, and bringing multiple defenders on the blitz from the same side.
Cover 3 Buzz
Cover 3 Buzz looks similar to the rolled down safety coverage we started talking about in this article, but there is a big difference in responsibilities.
Instead of sending the safety to play the curl flat defender, he's now playing hook to curl in the middle, and leaving the outside linebackers (or nickel defensive back) to play curl flat to the outside.
This allows the down safety (it could be either the strong safety or the free safety) to play closer to the middle and play physically with the crossing routes coming over the middle of the field.
Even if that guy never gets his hands on the route before the football is thrown, you've got someone playing in the middle of the field who has the ability to deliver a big hit and make the receivers pay for trying to catch the football in the toughest part of the field.
Pattern Reading in Coverage
Whether it's defending four verticals or any kind of crossing routes, one popular answer for coaches playing cover 3 is to play some kind of pattern reading coverage.
One of the most popular versions of this is called Rip/Liz coverage (You can see much more about this at the link).
Whether you call it pattern match, pattern reading, or something else, these kinds of techniques allow you to play an old school zone coverage, while still being able to cover all the routes that come into a specific area like a man coverage. It gives you the best of both worlds, and most defenses have these kinds of rules built into their calls, even at the high school level.
Nick Saban at Alabama is famous for his intricate pattern reading cover 3 defense, and was one of the early developers of the Rip/Liz coverage. Cameron Soran has put together a great analysis of the Nick Saban Coverages HERE.
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