The simplest definition of Cover 0, is the defense is playing man coverage on every eligible receiver. In the Nickle defense, all 5 DB’s are locked in on a WR/Slot/TE/RB. Whatever the offense sends out, the defense is covering man on man. If it’s base defense, then one of the linebackers will likely latch on to the RB/TE.
If you’re playing a team with a poor OL, a QB who can’t scramble and/or panics easily, or it’s an obvious run play, Cover 0 can be a powerful tool. With it being 5 on 5 from the secondary, it’s 6 on 6 along the LOS with one of their 6 being the QB that the defense is chasing.
The downfall is if a DB blows his assignment and his receiver beats him, you can have an easy TD. They’re also susceptible to crossing patterns and any route that the QB can dump the ball off quickly.
If the OL actually holds up, or the QB has some good scrambling skills, he can dump off a deep pass and there’s no help deep, or if the QB is a dangerous runner he can make the defense pay at that point, as well.
You need a great defense like Denver’s to pull this off. Not only does it take at least two great pass rushers like Von Miller and Derek Wolfe, but the corners need to be close to Aqib Talib and Chris Hariis, Jr., good. They not only must have the speed to follow on this man play, but know which eligible receiver to cover.
The upside is, it stops the run and terrorizes mediocre quarterbacks. They’re running for their lives or panic and dump the ball off too quickly for a bad pass. This formation, like on some Cover 1’s are known as, crowding the box.
The entire idea is to stop the run, or sack the quarterback, or take away the short interior pass.
Good quarterbacks/OC’s can pick a part a defense that tries this too often. This coverage is for special circumstances only. It could be third down, the offense is on the 40, and they need seven yards.
As in any coverage package, a defense can show the quarterback one coverage, but change it at the last second. On this, one or both safeties could drop back at the last second if they think the quarterback is going to try a pass. Defenses often show man and switch to zone, or the opposite. All of it is part of the chess game.
The first part of the graphic showcases the man on man function of each of the DB’s (Nickel Package shown) locking on one of the receivers. It also shows that the those not locked in on man coverage are rushing the passer.
The second part of the graphic shows the defense trailing/following/mirroring their offensive assignment. The X receiver runs a WR screen so that corner presses high. The LTE runs a post so the FS is running it with him. The RTE is running an out route, so the SS is following him along the way. The Z is running a fly route and that CB is running with him. The TB is running a flat route and in this case the Mike linebacker is trailing.
At times, teams can have a defender “spy” an offensive player. Any defense that is called, his normal responsibilities are out the window. He follows #x, wherever he goes.
An old story to expand on that. 10th grade, new football coach, who is an old school football coach. A extreme different type of coach that was previously at the school. Big game coming up with a rival. During the live version of practice, he stops the play. Grabs the Mike Backer by facemask and says “Son, I want you to follow #3 all night long. If he dives, you dive, if he sweeps, you sweep, if he goes to take a shit, you go wipe his ass.”
The principal is standing right there, and says “Coach, Language”. The coach, not even fully sure of what he had said, “Oh, I’m sorry. You go knock the toilet paper out of his hands.” Over the years he said the same thing, adding newer versions. “If he dances with his girlfriend….. you go kiss her”. (keeping it somewhat clean).
The point is, when you are spying on someone you follow them, you do what they do. If that coach were coaching the Broncos defense he might tell Aqib Talib to follow Michael Crabtree the whole game. No matter the call, you are on Crabtree… If he slants, you slant, if he runs a post, you post. If he shows you his chain, don’t rip it off of him this time, but stay on his ass.