Zone Coverage: Not as Simple as its Seams
by Mike Tanier
There are as many different variations in zone coverage as there are defensive coordinators at the pro, college, and prep ranks. This article is an overview of some general terms, rules, and concepts that are used by coaches at all levels. Before reading on, you may want to check out Chris Miraglia's article about the Cover-2 defense; we'll touch on some aspects of the Cover-2 here, but this essay focuses more upon Cover-3 rules, terms, techniques and assignments.
Cover-2, Cover-3, Cover-4
Zone coverage schemes are usually named after the number of defenders assigned to the deep zones. The Cover-2 is a two-deep zone, usually meaning that two safeties are responsible for deep routes. The Cover-3 is a three-deep zone. The Cover-4 is often called "Quarters" coverage because four defenders each handle 1/4th of the deep part of the field.
What about Cover-1? That's man coverage with a deep safety. No defender can control the entire deep part of the field by himself, so any time there's a single deep safety, other defenders will have to run with their receivers, hence creating man-to-man responsibilities.
And five is right out. Teams may use something akin to a five-deep zone against Hail Mary passes at the end of a half, but it generally isn't called a Cover-5.
Terms like Cover-2 designate the deep coverage, but many coaches will also refer to the underneath coverage when explaining a play. In Miraglia's explanation of the Cover-2, he diagrams a two-deep, five-under defense; some coaches call this a Cover-7 to denote the seven players who stay back in pass coverage. A typical Cover-3 defense includes four defenders underneath, while a quarters defense usually has three players in underneath zones.
Of course, the numbers change when a defense blitzes. Blitzers come from the underneath zone coverage, forcing their teammates to defend larger swatches of turf. As Miraglia points out, coaches like Tony Dungy don't blitz frequently out of their Cover-2 schemes. But coaches like Dom Capers and Dick LeBeau like to blitz from the Cover-3. Often, they'll send two players to blitz, leaving three defenders in the underneath zones (both coaches use a 3-4 alignment that gives them an extra linebacker to play with). That's the typical zone blitz: three deep defenders take away the big play, while five pass rushers force the QB to pass quickly.
Clouds, Skies, and Rolling Thunder
Just who plays deep in a three-deep zone? In "sky" coverage, the two cornerbacks and a safety cover the deep zones. In "cloud" coverage, one cornerback and two safeties handle the deep part of the field. That is sure to answer a question for some Madden and NCAA Live gamers, who often see the words "sky" and "cloud" used without explanation to denote defensive plays.
Cover-3 systems leave one player in the secondary free to either blitz or defend an underneath zone. Even if the extra safety or cornerback doesn't blitz, he can still step up and occupy a zone just vacated by a blitzing linebacker. Coaches then have incredible flexibility when disguising coverage, or when rolling the defense.
"Rolling coverage" means shifting the defense after the snap to provide extra support on one side of the field or another. In a cloud coverage scheme, the defense will often roll in the direction of the one cornerback who is not responsible for a deep zone. One safety shifts to a position behind that cornerback. The second safety moves to the middle of the field. The other cornerback drops back. A linebacker slides into the flat in front of the deep cornerback. Throw in a blitzing linebacker (with a cohort shifting into his zone) and the quarterback's read is very difficult: it's hard to tell who is responsible for which zone, and defenders suddenly appear in what should have been soft spots on the field.
Coverage is rolled for a variety of reasons: to protect a rookie cornerback, to provide extra support against a top receiver, or to help disguise a blitz. Coaches can cause further confusion by varying the size of the zone covered by each deep defender.
Quarters, Thirds, and Halves
In a Cover-2 system, the two deep safeties (or, often, one safety and one cornerback) are each responsible for about half of the field. In a Cover-4, the deep part of the field is generally sectioned into four equal parts. But in a Cover-3, coaches have some flexibility.
Usually, the deep part of the field is broken into three equal parts. But coaches can also design quarter-quarter-half schemes: two deep defenders are only responsible for 1/4th of the ground, while the third must take care of half the territory.
When Randy Moss lines up on the right side of the field, the opposing coach may be tempted to call quarter-quarter-half, with both a cornerback and a safety shifted to deep coverage on that side of the field. For quarterbacks who like to roll out or who prefer to throw to one side of the field, quarter-quarter-half coverage provides extra support on the side of the field that the offense is most likely to attack. In college football, where the hashmarks are further apart and the arms are weaker, the "half" defender can sit back and worry about difficult across-the-body passes while two teammates handle more likely pass targets.
Quarter-half-quarter coverage is also possible: typically, the two cornerbacks deal with 1/4th of the field near the sidelines while a rangy safety handles the deep middle. When the opponent likes to throw lots of fade passes, fly patterns, and sideline routes, quarter-quarter-half coverage can force those pesky receivers to come across the middle.
Seams and the No-Cover Zone
There are theoretically three seams in a two-deep zone. One begins about 14 yards down the middle of the field, extending to a depth of about 20-25 yards. The other two are at the same depth along the sidelines. These seams lie behind the underneath coverage but between the safeties (or the safety and the sidelines).
In reality, that middle seam is disappearing at the pro level. Safeties and linebackers are so fast that someone is going to converge on that 18-yard pass over the middle unless the offense puts some effort into creating some space. For example, one receiver could run a deep post, forcing a safety to drop back and allowing a second receiver to enter the seam a split second later. The sideline seams are still common attack points for the offense, but 20 yard passes along the sidelines aren't easy to execute.
A Cover-3 zone has two seams. Each begin about 15 yards from the sidelines and are about three yards wide. Like the seams in a Cover-2, these seams extend from a depth of about 14 yards to one of about 25 yards. When you hear that a tight end or slot receiver ran a "seam route", it means that he ran a simple fly pattern into one of these hard-to-get-to cracks in the defense.
In addition to the seams, zone defenses have a no-cover zone. This is a three-to-five-yard zone extending out from the line of scrimmage and running the width of the field. No defender is supposed to cover a receiver (usually a running back) who is sitting in the no-cover zone.
Does this mean that zone defenses are meant to allow an endless stream of three-to-five yard passes? Not at all. Underneath defenders are expected to read the quarterback, anticipate the throw into the no-cover zone, and beat the ball to the receiver. If the defender jumps the route and picks off a pass, he could easily score. He's in good position to tip the ball even if he doesn't intercept the pass. At worst, he can make a tackle for a four-yard gain. Had the same defender camped out in the no-cover zone with his receiver, his zone would be stretched thin, and he would be vulnerable to a move up the field.
If you ever tried to play a zone defense in a pickup game, you probably realized right away that it's hard. In basketball, setting up a 2-3 zone is pretty simple: the space is limited, so it is pretty easy to pick up guys in your zone. In football, with all of that space, you may find yourself defending an empty patch of turf while receivers catch passes in front of you, next to you, and behind you.
Rams fans can relate. Their young linebackers had a hard time with the intricacies of zone coverage last season, allowing lots and lots of receptions by tight ends and running backs. It wasn't that Robert Thomas and company weren't fast enough to stick with their receivers. Rather, the problem was that they were too inexperienced and indecisive to read and attack pass routes.
That brings us to the key element of zone coverage: defenders must break on the ball before the pass is thrown. Any defender who sits in his zone and waits for the quarterback to release the ball before making his move is a cooked goose. He must watch the quarterback and follow the progression of the pass routes in order to determine where the pass is going to be thrown, and he had better be moving when the ball is released.
Remember that zone coverage is not man coverage: a linebacker assigned to the "hook" zone (the region about 7-10 yards from the line of scrimmage just outside the tackles) cannot rush out to blanket a tight end who enters his territory. If he does, he'll be in no position to stop the running back executing an angle route into the same zone or the wide receiver running a slow drag from the other side of the field. All three players will be that linebacker's responsibility at some point in the play, so all he can do is drop into his zone and stay alert.
That means that the tight end could run an eight-yard pattern, curl to face the quarterback, and stand there with the linebacker six yards away. Essentially, the tight end is open, because the linebacker is on the lookout for other receivers. If the quarterback decides to throw to the tight end, the linebacker has to beat the ball there. That only can happen if he anticipates the pass.
But how can defenders perform these nearly psychic readings? They watch the drop of the quarterback, knowing that shorter drops lead to shorter passes. They read his eyes. They watch the cock of the shoulders: longer passes require the quarterback to dip his back shoulder. They learn the difference between a passer's pump-fake and his throwing motion, and they look for clues, like patting the ball, that indicate that the quarterback is ready to release.
The pass routes themselves provide further clues. Offenses use routes in combination to beat zones. That eight-yard curl by the tight end is often accompanied by an angle route or flat route by a running back, with a deep post route by the receiver on that side of the field. A savvy defender can figure out what the defense is up to and follow the same reads the quarterback makes.
All of this reading and reacting requires a lot of gray matter. It's an oversimplification to say that man coverage is all about athletic ability, while zones are all about intelligence. But there is more than a bit of truth in the statement. Excellent athletes have proven to be hopeless in zone coverage because they don't react quickly (Derrick Gibson of the Raiders is an example), while slower defenders with tons of experience can be very effective.
Summing It Up
The basic mathematics of football hasn't changed in decades. There are five eligible receivers on offense. Assuming that the defense reserves five players to cover them (in man or zone), that leaves six free defenders. At least three will rush the passer, probably four. That leaves two free hands.
Those free players can blitz. They can drop into zones. They can double cover receivers. They can rotate, rushing the passer while a lineman drops into coverage or sliding into a deep zone while a cornerback blitzes.
The defense can play two-deep, five-under, chocking out the short passing game. It can play four-deep, three-under, a great defense for a two-touchdown lead in the fourth quarter. It can play Cover-3 Cloud, with a cornerback and linebacker blitzing, a defensive end dropping into a flat zone, and the secondary in quarter-quarter-half responsibility. Or they can man-up, let the free safety roam, and send one linebacker on a blitz.
The only limits to the variety of coverage types are the imaginations of the coaches and the physical limitations of the players: Hollis Thomas can't drop into a deep zone. Essentially, anything is possible. That's why quarterbacks spend hours breaking down film, and why players on both sides of the ball have to be a whole lot smarter now than they used to be.
32 comments, Last at 16 Aug 2010, 11:40am
#1 by kleph (not verified) // Aug 15, 2005 - 12:12pm
mike tanier is my new personal jesus.
#2 by Mike B. (not verified) // Aug 15, 2005 - 12:47pm
Awesome stuff. I'm guessing the Rams' ridiculous success attacking zones - the phenomena of seeing Bruce or Holt standing wide open 14-18 yds deep - is because of the speed of the receivers and the "clearing out" routes they run. Maybe people don't give coaches and coordinators enough credit...
Playing D has come a long way since I was in High School.
#3 by Ray (not verified) // Aug 15, 2005 - 1:47pm
Great article. Now I just have to figure out how to apply that to NFL 2K5...
#4 by CaffeineMan (not verified) // Aug 15, 2005 - 2:57pm
Three shall be the number thou shalt count, and the number of the counting shall be three. Four shalt thou not count, neither count thou two, excepting that thou then proceed to three.
Oh, and, yeah, excellent article Mike. :)
#5 by Teddy (not verified) // Aug 15, 2005 - 3:26pm
I usually only chime in with bad jokes, but that was a fantastic article. Thanks.
#6 by Independent George (not verified) // Aug 15, 2005 - 4:17pm
This is one of the things that made Lawrence Taylor so amazing at linebacker. He was most famous for being a pass-rusher, but I also remember him regularly batting down balls on short patterns to the weak side (often after faking the blitz). The funny thing is, he was also notorious for either missing or sleeping through film sessions; he did it all on pure instinct.
#7 by jim haslett (not verified) // Aug 15, 2005 - 4:34pm
Mike Tanier, would you like to coach my defense this year?
#8 by S Baker (not verified) // Aug 15, 2005 - 4:53pm
This article rocks. All the FO "Football 101" stuff is terrific, and fills the void of actual information almost always ignored by sportswriting and sportscasting. Any chance we could get some accompanying diagrams in future features? Sweet job.
#9 by Perrin (not verified) // Aug 15, 2005 - 5:21pm
Great article, like all the 101 articles.
#10 by Vince (not verified) // Aug 15, 2005 - 5:42pm
Re #2: As much as people like to rag on Mike Martz, he's still right at the top of the list of designing and planning on offense. I don't know if I'd want him to be my head coach, but I'd take him as my offensive coordinator with a huge smile on my face.
#11 by MikeT (not verified) // Aug 15, 2005 - 8:00pm
#7: Sorry, Mr. Haslett. I am trying to hold out for a job with an NFL team.
#12 by ABW (not verified) // Aug 15, 2005 - 8:17pm
I'd just like to give some props to Mike T and the rest of the Outsiders for this series of articles - they are amazing and they really help those of us who didn't grow up playing football to understand and appreciate the game more. Thanks guys, and keep up the good work!
#13 by JPS (not verified) // Aug 15, 2005 - 8:42pm
Not mentioned here, and making the defense's job even harder, is that passes are typically thrown after only three seconds, and much sooner with some QBs. So take all the responsibilities for teams of pass defenders mentioned in this great article and cram it into just a few heartbeats. Whew!
#14 by Ron Mexico (not verified) // Aug 15, 2005 - 10:46pm
Wow! Thanks for this article. I'm sure this will help me figure out how to throw against zone coverage a whole lot better this year.
#15 by Gatts (not verified) // Aug 16, 2005 - 8:46am
#7: Sorry, Mr. Haslett. I am trying to hold out for a job with an NFL team.
#16 by Israel (not verified) // Aug 16, 2005 - 11:56am
Funny - I just put the Steelers-Eagles game on Field Pass. The game has barely started and Tunch is into an explanation of quarter and cover 3. And having read your article earlier today, I actually understand what he is saying.
#17 by James, London (not verified) // Aug 16, 2005 - 1:26pm
This is another terrific piece, and you're right, when I next play Madden or listen to commentary refering to 'cloud' or 'sky' I'll know what it means.
Can I suggest that you collect these minicamps together (I assume there will be more to come) and publish a 'football 101' with (or in) next years Prospectus? I loved the Prospectus by the way, even if Amazon sent it acroos the Atlantic by canoe.
#18 by BC (not verified) // Aug 17, 2005 - 12:00am
It's simple to remember the difference between Cloud and Sky. C is for cornerback and S is for safety. Cloud has two corners and Sky uses two safeties.
#19 by Dan (not verified) // Aug 17, 2005 - 3:37am
BC is the devil!
#20 by dryheat (not verified) // Aug 17, 2005 - 9:18am
Except that according to the article, you've got it backwards. So remember the Cloud stands for cornerback, not cornerbacks.
#21 by azibuck (not verified) // Aug 17, 2005 - 10:23am
This is a good article. But, where is the Football 201 stuff?
#22 by BlueStarDude (not verified) // Aug 17, 2005 - 12:56pm
I was going to say what James already said in #17 - you should collect these for your next book. Great stuff.
#23 by stan (not verified) // Aug 17, 2005 - 3:56pm
Re: Sky and Cloud
The terms are used to identify which defender has responsibility for outside run support (sky for safety and cloud for corner). The explanation in #18 is wrong. For example, a coverage such as 2 Sky will invert the safety and the normally clouded corner to the strong side of Cover 2. Thus you have a strong side corner taking deep responsibility, a strong side inverted safety who will work to the flat, a deep safety weak and a clouded corner jamming and funnelling on the weak side before taking the flat.
Don't try to make the terms mean more than they are intended to mean.
By the way, the reason a defense would do this is to throw off the conversion routes of the receivers (as well as the QB's read). The defense looks like cover 3 to the strong side, but it isn't.
#24 by stan (not verified) // Aug 17, 2005 - 4:04pm
Note also that zone techniques can vary significantly. Some coaches want under defenders to "wall" a numbered receiver, e.g. in cover 3 the Will LB would wall the most outside route weak, Mike would wall #2 weak, Sam walls #2 strong and Strong safety walls #1 strong. The drop is aimed to fit inside and under the receiver's break. It is thus adapted to the route. (Not to be confused with pattern reading, however).
In contrast, the original drop technique (still used by many) is to have the defender drop right to the middle of his assigned underneath zone, read the QB and break on the ball without reference to the routes being run around him.
#25 by ABW (not verified) // Aug 17, 2005 - 5:49pm
Stan, I'm a little confused. Can you explain the 2 Sky coverage you describe in #23 a little more? Is a "clouded corner" one who has run defense responsibilities? Do the terms sky and cloud only refer to strong side run support, so that the "sky safety" or "clouded corner"(if I'm using those terms right) would have responsibilities for runs outside of the tight end? I'm not very knowledgeable about these things, but I'm trying to learn, so please bear with me if I'm asking stupid or nonsensical questions.
#26 by Countertorque (not verified) // Aug 18, 2005 - 3:49pm
MikeT, can you write an article explaining all of the receiver routes? I understand some of them, but not all. I'd really like to be more knowledgeable about that.
#27 by Hook (not verified) // Aug 19, 2005 - 5:37pm
I'm currently working on a football management simulator, and I'm absolutely appalled at the lack of basic, good solid introductory books about football. Something beyond 'football for dummies' but a lot simpler than the various compilations of essays/play descriptions by various coaches.
I'd love to have a list of the top 10 most common plays out of various formations with a description of everyone's responsibilities. Sadly, Madden probably does the best job of showing you this stuff, but they don't bother telling you what each play is designed to do.
#28 by Tim L (not verified) // Aug 22, 2005 - 9:55pm
Loved the article, Mike.
#29 by Bulldozer36 (not verified) // Aug 24, 2005 - 1:18am
Its articles like this one that I can bookmark and send to my friends overseas so theyll better learn the intricacies of this game.
#30 by MikeT (not verified) // Aug 24, 2005 - 4:10pm
Thanks, Stan, for those clarifications on sky and cloud and Cover-3 wall-off drops. It's amazing how complicated this stuff is. When I hear "rookie LB such-and-such is having trouble learning the system", I don't assume that he's dumb or not trying anymore.
This was the last minicamp of the year! It's time for real football. I'm guessing we'll be whipping up a fresh batch next season, probably with a lot more offensive stuff.
#31 by Lu (not verified) // Oct 13, 2005 - 12:38am
"Offenses use routes in combination to beat zones. That eight-yard curl by the tight end is often accompanied by an angle route or flat route by a running back, with a deep post route by the receiver on that side of the field. A savvy defender can figure out what the defense is up to and follow the same reads the quarterback makes."
One of the absolutely most important points that can be made about Zones. Generally, it takes a REALLY heady defender, or at least one that has been coached up during film, to be able to stop these combination routes.
This is what I get at when I say that offenses can really take advantage of a 3-Wide formation. It's a formation that creates a lot of opportunity for combination routes (smash, flood, etc) on one side, with a clearout pattern across it, or underneath it (flats).
As for the discussion of Zones, I'm assuming you simply wanted to give a basis...but may I add, when discussing Cover 3, the most crucial factor of that zone: the area (or distance) where assignments transfer from player to player.
Yeah, it's important to explain that the Zone creates 2 seams, etc etc, but its farking CRUCIAL where Cover 3 actually turns into a cover assignment. Again, you obviously are creating a basis for the explanation, but if it were just that simple team's would simply flood the hell out of a 1/3, of even one of the 1/4+ 1/4 variations (considering there wasn't an assignment exchange discussion).
In A LOT of Cover 3's, the yard area/distance was 8 yards. This was an absolutely crucial point because if a WR lined up in front of a Corner in Cover 3 Sky (sometimes called "drop") crosses that 8 yard marker, it basically becomes HIS assignment, and it's then man coverage.
The Safeties must be unbelievably aware of that 8 yard marker, and have good communication with the Corner(s) because what a lot of offenses will do is run a smash combo route, consisting of a strategic 6-8 curl by the WR, and a Corner route right over the top of that by an inside WR or a TE. This is just one example.
There are a million intracacies, but failing to mention how the ultimate assignments get made, and this "area," basically leaves a crucial point out, especially when talking about Cover 3. Pretty solid basis and outline of explanation though.
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