Last week week we wrapped up our look at the defensive front seven, and started our look at the personnel of the defensive secondary.
This week we will be moving on from secondary personnel to the coverage schemes the personnel play in. Coverage schemes are referred to as "Coverage Shells." It can be a bit confusing, but the easiest way to think of them is as shells around the defensive front seven. Coverage shells are typically named by the number of players covering the deep part of the field. Not only can that tell you a lot about the coverage techniques being played, it can also tell you about the defensive play call.
We'll start with the two simplest, and most aggressive, coverage shells.
As I mentioned above, coverage shells are typically named for the number of players covering the deep portion of the field, and for "Cover 0," there is nobody covering deep. Cover 0 is straight man coverage, with five defenders covering the offense's five receiving options
While every team plays Cover 0 at least some of the time, there aren't any (to my knowledge) who use it as a part of their base defense. It's, quite simply, too risky and requires more talent in coverage than most teams have on their roster. It is a tall order to ask a defensive player to line up in man coverage every play, which is why the players who are capable of that are so difficult (and expensive) to find.
However, playing Cover 0 opens the defense up to bring extra pressure on the passer. It is a calculated gamble (that we'll get to in more detail much later), because with no deep coverage, Cover 0 can be vulnerable to giving up big plays, screen passes. But by leaving two defenders without coverage duties, the defense wins the numbers game with six rushers to just five blockers. That is assuming, of course, all five receiving options release into routes. The offense can counter this by calling a six- or seven-man protection -- usually leaving the running back and tight end in pass protection.
If "Cover 0" means that there are no defenders covering the deep part of the field, then it should follow that "Cover 1" has a single player defending the deep part of the field. In this case, the free safety is playing zone coverage over the deep-middle part of the field, often referred to as "Center fielding," to blatantly steal a term from baseball. But, it's an accurate term for what the position requires. Like a center fielder in base ball, the free safety in a Cover 1 shell needs to be athletic enough to cover a large amount of space, and able to accurately diagnose where the ball is going as quickly as possible.
While the term "Cover 1" doesn't directly relate to the coverage being played closer to the line of scrimmage, it's generally assumed that the other secondary players are in man coverage.
The Cover 1 shell is marginally less aggressive than the Cover 0, but at the same time seeks to address some of the drawbacks of straight man coverage. By leaving the free safety back in zone coverage, the defense can double team the offense's best player while having every receiving threat covered, and still able to bring five pass rushers. In the diagram above, I have the defense in a "Base" package, with three linebackers, two cornerbacks, and two safeties. The offense likely has an advantage being in "11 Personnel," and in a real game they would likely use a nickel package.
Defensive sub packages generally take a bigger, slower player (such as a linebacker or defensive tackle) off the field, in and replace them with a third corner or safety -- totaling five secondary players, and a nickel being worth five cents, this should be obvious. The "Dime" package has two "nickel" players -- or a defensive end to rush from a defensive tackle position. Ideally in this particular situation, the defense would have a slot corner such as Trevin Wade, or a third safety like Nat Berhe, covering the slot receiver, while the strong safety (Landon Collins) covers the tight end. To get the third defensive back on the field, the Giants would likely take the middle linebacker (Jasper Brinkley, for the sake of argument) off the field.
However, for our purposes, the personnel package doesn't really matter. We just want to show assignments and concepts.
Also, in the diagram above, the linebackers don't have defined assignments. Their specific assignment will largely depend on the play call. The linebackers could drop in to shallow zone coverages to help defend against the tight end or running back running a quick route to beat any pressure that may be coming the quarterback's way, they man coverage on an offensive player, they may be sent after the passer as a blitzer (more on blitz concepts much later), or any combination of the above.
With the right personnel, Cover 1 is a formidable, yet elegantly simple, defense. It isn't without weaknesses, however. Because of its reliance on man coverage, Cover 1 can be beaten with pick plays ("Pick" or "Rub" routes are routes that can force separation in tight coverage by forcing a defender to run around another player as routes cross), screen passes, play-action passes, or by having more talented players than the defense can cover man-to-man.
Next week we'll be adding another layer (or two) of complexity as we look at Cover 2 and Cover 3 shells.