NFL schemes can sometimes be very fascinating, while other times they’re incredibly dull. Coaches are risk-averse and play it close to the vest. It’s almost as if they’re afraid to deviate from established trends and from what the rest of the league is doing, because any one play can cost them their job. One bad pass play can cost a team late in the game and put the play caller on the hot seat. The wrong coverage called on a chain-extending fourth down can lead to many questions about the defensive coordinator. All this begs the question: why are schemes so fascinating then?

The truth is it’s because of how they are presented. Presentation is everything in the NFL for two reasons: 1) the resulting concept is the same thing everyone else runs and 2) it’s sometimes full of false looks that screw with the quarterback’s keys while other times, it’s a what-you-see-is-what-you-get kind of thing. This Sunday, the Arizona Cardinals play the Minnesota Vikings, and each team uses similar coverages, but present them completely different.

Arizona’s defense, which is one of the league’s best, has its roots with Dick LeBeau, the legendary Pittsburgh Steelers shot-caller. Defensive coordinator Ray Horton worked with LeBeau, who has specialized in the use of triangles to stop the opposition for many years, and Horton brought over much of what he learned from LeBeau.

Horton’s defense is based out of the 3-4, but the Cards line up pre-snap using a multitude of fronts that create quite the football kaleidoscope. A turn may show a snapshot of a three-man front, while another turn results in just two down linemen, and another shows a front of four.

2-man front and moving parts.

Conversely, the Vikings’ kaleidoscope is much less dynamic as the defense bases out of a four-man front — a 4-3 to be specific — and it primarily serves as the defense with Under and Over fronts. In layman terms, an Under front consists of the strong-side guard being uncovered with the strong-side linebacker across the tight end while in an Over front, the strong-side guard is covered. In fewer words, the Vikings scheme of choice is the Tampa Two, a defense that uses Under and Over fronts.

Over front.

But what makes these two defenses interestingly different is their coverage preferences. As noted, the Vikings are not as dynamic defensively as the Cardinals, and one of the reasons is not only their usage of fronts but also their coverages. They play out of the Cover-2 variation — again the Tampa Two, which is essentially a three-deep coverage that has the middle linebacker (“MIKE”) dropping down the “pipe” or seam of the defense while four defenders under sprint to their landmarks at the when the football’s touches the quarterback’s hands.

Tampa Two

The two deep safeties are responsible for their thirds of the field which lie over the cornerbacks, who are charged with covering the flats. Although the Vikings base out of the Tampa Two coverage, it should be noted that it’s not their only coverage — a mistake many make.

They do play a variety of coverages other than this one, such as Cover-1 (Man-Free) and Cover 3. Both of these coverages consist of one-deep safety, which they present from a two-deep shell and rotate down as the snap nears. This can be witnessed in any game, and here’s an example from Week five against the Tennessee Titans.

Cover 3.

The Vikings don’t do much rotation before the snap unless it’s their safeties. In contrast, the Cardinals rotate a lot, moving their players to get to the desired coverages. As I wrote for The Boston Globe during the week of the Patriots-Cardinals matchup, the Cardinals use a variety of coverages in their defensive backfield:

The coverages used include Cover 0 (man with no safety help), Cover 1 (man with one deep zone safety), Cover 2 (5 under, 2 deep zone), Cover 2 Man (2 deep, man under), Cover 3 (4 under, 3 deep), Cover 4 (Quarters) and what some call Cover 6, which is a blend of Cover 2 and Cover 4.

Arizona will show more looks to the offense to confuse the quarterback and offensive line and then get to their intended coverage. On one particular play against New England, the Cardinals defense showed an overload blitz from two sides — the center and left — from a three-man front, which would amount to a  total of seven defenders rushing. However, they quickly backed out and only sent four, and then played the same coverage that the Vikings did above (Cover 3). Here’s how:

Cover 3.

Even though these two defenses play a similar coverage, they get to it through vastly different paths, and that’s what makes schemes so fascinating.

The Vikings prefer to play less coverages than the Cardinals. They also do less disguising, but they’re more willing to send the blitz, such as a safety or double A-gap blitz. Regardless, both defenses have had a fantastic first six weeks to the start regular season by ranking in the top ten in points allowed, and they should force turnovers in tomorrow’s matchup.