Author's note: for whatever reason, I found writing about the passing game to be a little tougher in the x's and o's style of these pieces than other aspects of the game. Probably because there are generally more moving parts, and less clear camera angles. So, grain of salt on my analysis and all that. Enjoy.
Cover-2 defenses can be such a pain. And they are ev-ry-where. If your team isn't running cover-2 as its base defense (See: Iowa, the Chicago Bears, and the Indianapolis Colts in the past), it's certainly using it in some capacity. And while all your short routes, and your quick passing game, are getting swallowed up by the defense's five shallow zones, those two safeties are sitting deep in that high shell, taunting you until you make a mistake. It's a time tested scheme, that's deployed because it works.
But like most everything in football, every move by the defense has a corresponding counter from the offense (and vice versa). In this case, you can crush cover-2, both the more common cover-2 zone, as well as its variant, cover-2 man, by pulling the classic pass play 'three verticals' out of your playbook. If the defense is running cover-2, and you recognize it, three-verticals will ruthlessly exploit that scheme's weak points for potential big plays. What looks like, "F*ck it, we're going deep." is actually part of a cat and mouse game between offenses and defenses.
What is three verticals?
Like it sounds, it involves sending three of your receivers deep down-field. Due to the way it requires you to space the field, it is typically run out of three wide receiver sets either 2x1 (two receivers to the left and one receiver to the right) or 1x2 (one WR to the left, two WR to the right) sets. But it's equally viable in 221 (2 WRs, 2 TEs) or 212 personnel (2 WRs, 1 TE, 2 HBs). The formation is flexible, adding to the power of the play. But the constant remains: three vertical routes down-field.
But what vertical routes do the receivers run? Go routes (or 'streak' routes), where the receiver just runs straight ahead as fast as he can? Well, maybe, but not typically. What you'll usually see is the two outside receivers will (at least initially) run deep corner routes towards the sideline, while the inside receiver (or TE) will run a deep post route. As I'll get to in a bit, this best exploits the weaknesses of a cover-2 defense.
Why is three verticals so good against cover-2?
At the heart of it, it's simple arithmetic: 3>2. That is, the two deep defenders of the cover-2 get overwhelmed by the three deep routes and at some point those two have to make a choice that leaves someone either in single coverage, or wide open.
To understand why this is, let's look at the basics of cover-2 a little closer:
Via Smart Football, though credit for the picture goes to Ron Jenkins, according to that link
Because those five underneath zones can so well cover the field from the line of scrimmage to about 10 yards deep, three verticals bypasses that line of defense to attack the comparatively weak, deep 1/2 zones (where each safety is responsible for an entire half of the field).
And more specifically, it targets the very weakest areas of the deep halves, what that diagram calls the fade areas, and the deep middle.
HASTILY DRAW MS PAINT REPRESENTATION OF THE PLAY AHOY!!!
On this play, 2 fade ares are attacked. The third over the middle is neglected in favor of tricking the SS.
The fade areas are marked in these blue boxes. This play essentially keys off of just one player: the strong safety (the safety to the upper right with the arrows pointing away from him). He's responsible for covering two of these 'weak points' and his choice dictates much of the read for the QB. If he keys on the slot receiver, the QB throws the fade to the right. If he keys on the fade, the QB throws the deep post or in-route over the middle.
This play is another example of the versatility of MSU's pro-style offense and of players like Brian Linthicum. This is 221 personnel, a flexible grouping for the MSU offense. If both TEs were put on the offensive line and Caper was slotted behind Cousins under center, you'd probably guess a run was coming. But here, without needing to sub in new personnel, MSU can put Cousins in the gun, split Linthicum into the slot, and now they have passing spread principles at zero 'cost' in terms of tempo or predictability.
Martin and Cunningham are the outside receivers. The OSU cornerback at the bottom of the screen is showing blitz, a clever cover up by Ohio State (if he blitzes it is exceedingly likely that OSU would play a deep cover three shell with the two safeties and the cornerback at the top of the screen. Such a coverage change up would limit, possibly severely limit the effectiveness of a play like 3-verticals).
But the corner doesn't blitz, and both OSU CBs press the outside receiver in an attempt to reroute them, a tip that it's cover-2 coverage. Another tip comes from the way the linebackers drop immediately into coverage, particularly the MLB flying back to cover the middle of the field.
The bottom OSU corner presses Martin to reroute him from the outside-in, towards the middle of the field,
but basically plays the matador here, letting Martin blow by him. His primary concern is making sure no funny business happens in this shallow flat zone, and he'll let the safety clean up Martin behind him. Moreover by this point, he can see Cousins is either throwing to the right side of the field, or he's about to get flattened.
At the top of the screen (ESPN's camera angle here is the worst. THE WORST.) the other corner jams Cunningham from the inside-out, towards the sideline. This is an interesting choice on his part, for reasons I hope become clear. These jams are supposed to give the safeties time to react to the WRs routes. It half works.
The offensive line slide protects here, letting a DE come through the line unblocked while the rest of the offensive line moves to the right to form a stronger pocket to that side of the field. Caper, the running back, really needs to properly cut block this onrushing lineman to make this protection scheme work, but he fails and the DE leapfrogs his way into the backfield.
On the other side, John Simon negates much of the point of the slide by beating a double team with a nice spin move. Someone better be open because Cousins needs to get rid of the ball, like, now.
Though we can't see what's going on, it's pretty safe to assume OSU's deep free safety has picked up Keshawn Martin deep at the bottom of the screen. But a key to this play is giving receivers freedom to option their routes depending on what the defense does.
Brian Linthicum sees early on that the safety is staring him down, so rather than keep running the deep post, he cuts his route short at about 15 yards and runs a simple, right angle, 'in route'. OSU has the weak-side linebacker covering Linthicum underneath and the middle linebacker dropping deep to cover him over the top. This 'in route' is a decoy to keep the safety's attention on him for just a few more seconds.
Meanwhile Cunningham has taken advantage of the fact that the OSU corner takes a bit too long to get out of his back pedal, and the fact that the corner rerouted him to the outside, to find space down the sideline.
The OSU safety might think he's doing the right thing in making sure Linthicum can't run past these LBs into the deep middle of the field, but the second Cunningham gets outside and past his CB,he needs to be sprinting for the sideline to break up the pass that's coming to the fade zone. If you look up at the MS paint picture he needs to be moving in the direction of the grey arrow, but he also needs to make sure the TE can't get in behind him. This leads to him lingering too long in the direction of the brown arrow. This tug of war on a safety's positional responsibility, and mental state, makes this play work as well as it does.
Because he keeps his eyes on Linthicum for several seconds too long, by the time he realizes his mistake it is way, way too late for him to do anything about it.
Cousins, as he is about to get hit, manages to put the ball basically right on the money. Cunningham slows his stride a bit to catch the ball, and then is able to race about 25 yards down-field before anyone can catch up to drag him down.
Yessir. Thanks Youtube user 'JMPasq':
What can you do to stop Three Verticals?
The easy and quick solution is to change your zone from cover-2 to cover-4, something you can do without changing your defensive personnel on field. This means that those two fade areas are now covered by the CBs, and the deep middle zone is patrolled by both safeties. A swap to cover-4 flips the arithmetic deep down field from 3 v. 2 for the offense to 4 v. 3 for the defense. The infuriating deep throws into double coverage against Nebraska were in part due to MSU trying to throw three verts against cover-4, when they thought Nebraska was in cover-2.
What can the team running Three Verts do to stop this adjustment to Cover-4?
Well, if the corners are bailing out to cover those deep zones, it's the job of the WRs and the QB to recognize that mid-play, and take advantage of those 'choice routes' to have the receivers run curls. or hooks, or outs into the now (hopefully) vacated flats for a 7-10 yard gain.
This requires your QB and WRs to be on the same page, and changes the read from the safety to the corner. This can be difficult to do on the fly, which can sometimes explain those plays where your QB overthrows or under-throws your receiver by a significant distance.
Three verticals is a classic hard-counter to cover-2 coverage, and if you can properly identify in cover-2, and then execute this fairly simple play, you can run it again and again for big gains down-field. It puts an enormous amount of pressure on the play-side safety to cover both of the vulnerable deep zones at the same time, and more often than not, the offense is able to take advantage of that.
More reading/video on the subject: