For the last several years, the passing game has served to replace much of what the run game used to accomplish for teams. Single-back and eventually full blown spread attacks begin to find new uses for smaller, shifty athletes rather than simply handing them the ball. Rather than serving as the "pitch-man" or "change of pace" back, coaches began to put them in the slot.
These players, many of whom might have been stars in the triple-option era but not in the age of the I-formation, began to re-emerge as coveted athletes for use in quick passing game concepts. When fans think of slot receivers today they tend to think of shorter players with great start/stop speed that are impossible to cover up and are always open in space on 3rd down.
However, I-formation tactics are starting to come alive again within spread programs. Those are, namely, attacking the line of scrimmage with lead runs before chucking the ball vertically to receivers on the outside or up the seam.
Teams have discovered that this aggressive approach to moving the football can be attained with spread personnel from formations like the pistol, or the gun:
The change for the slot receiver is this: the ideal complement to a power running game with a lead blocker sharing the backfield is a vertical passing game that can punish teams for bringing safeties into the run game.
Indeed, the proliferation of spread-option offenses has resulted in quarters coverage becoming everyone's favorite base defense for the way it "gets nine defenders in the box". Well, it can be risky to have so many players gearing up to fly downhill and stop the run if they have to worry about vertical passes.
Hence the rise of the deep threat at slot receiver.
Profile of a killer
The brilliance of the spread-I is that there's no need for a dual-threat TE who can block DL from an in-line position on one snap and then threaten the seam on the next, such players are very hard to find as the supply of burly, athletic, tall, and skilled people in this world is fairly limited.
Teams have found work arounds and love to use versatile players that are big match-up problems for their ability to block or catch short routes. However, while that's useful for ball-control tactics it's not as useful for delivering kill shots over the top against quarters teams. Iowa State has one of the best such players in the league in EJ Bibbs but are ranked 65th in the nation in offensive S&P because it's hard to score with ball-control passing to big targets.
Like the B-back, the vertical slot receiver can be much easier to find than the elite TE, but you are capturing the more dangerous element of what that elite TE brings to the table, the ability to throw the ball up the seam for points.
As far as his profile, he needs to be tough enough to catch the ball over the middle, it's best if he's a larger target that's easier to hit when the QB is throwing over linebackers' heads although this needn't necessarily be the case, and he needs to be fast enough to cause problems for a safety in coverage.
That's it. That describes an enormous percentage of wide receivers.
Attacking the deep middle
Here's one of the more popular quarters coverage alignments that gets the free safety and nickel involved as run-force/cutback defenders who can cause big problems by allowing a defense to outnumber the run game:
The most obvious way to attack this coverage is with the "Y" slot receiver against the strong safety. On a running play, that nickel and the linebackers are going to be sucked in or else the defense risks getting gashed by a lead run thanks to the H-back.
Quarters coverage can draw up any number of sound defenses for handling spread passing concepts but on play-action there's no changing the fact that the nickel is unable to both support the run AND protect the strong safety by seriously disrupting the slot receiver's route.
That's Baylor senior Clay Fuller hauling in that catch. At 6-2 with good speed and experience in the Bear offense, he's a valuable player but NFL teams aren't going to knock down his door to draft him. There are many Clay Fullers out there in the world that can do damage with these concepts.
On non play-action routes, you need more quickness and skill at the position since the linebackers are then available to help funnel the receivers upfield in a way that helps those poor safeties. The best play in these instances is, of course, four-verticals. But there are other concepts out there that also set up slot receivers with vertical option routes that can get pretty nasty to defend:
This one is called "Houston" and is a Dan Mullen/Urban Meyer favorite. Run from a spread-I formation, the slot receiver runs upfield on a vertical stem and runs a go route if the defense has a safety in the middle of the field or if there are two deep safeties, like here, he'll run a post route.
It takes longer to develop and requires some skill and speed by the slot in crossing the face of the strong safety, but it's a pretty feasible route for a good receiver to run and easier to connect on than something like a deep fade.
With a killer receiver in the slot, spread teams have a lot of ways to attack the deep middle of many teams' favorite defensive coverages and turn it into a soft spot. That's pretty difficult to counter for a defense, especially if the run game is also good.
Attacking the sidelines
There are other benefits and options for using a vertical slot receiver to attack downfield, and those include increased opportunities for attacking the sidelines.
Take the above "Houston" concept for example, that strong safety is generally reading the slot receiver and if he goes in or out rather than running a vertical route stem, he can help double team the X receiver. If he is contending with an option route by the slot receiver? Not so much.
You get the same effect with concepts like "4-verticals." If you make the safety cover a vertical route he's A) outside his comfort zone and not doing what he does best and B) he's not helping the corner over the top.
If a team has great outside receivers, 4-verticals is going to potentially give them a massive match-up opportunity on those cornerbacks who have to play without safety help.
You can also use slot receivers to attack the sidelines and/or get your outside receivers a chance to run circles around a safety in the open field.
Concepts like "smash" allow the slot receiver to attack the sideline and try to beat the safety with route running and speed deep:
Some of these routes require true arm strength and accuracy from the QB to deliver the ball, others simply require vision and touch depending on if the QB is throwing the receiver open or trying to drive the ball through a window.
If a team can finally cause the defense to give up on quarters coverage and play some kind of single deep safety coverage it's time to switch things up with the switch route:
The goal is to get a "rub" on the defenders playing man coverage to free up the "X" and "Y" receivers to find open grass. Once they find that open grass, they'll generally have options to allow them to settle in or run towards open spaces.
A deadly and feasible concoction
Essentially what's being discussed here is a combination of the I-formation with the run and shoot. Common adjustments to defending spread-option teams, like quarters coverage, can leave a team vulnerable to old school I-formation tactics that bring play-action and lead runs to bear.
But the problem with the I-formation was always the complicated reads that result from clustering so many players in the middle of the field, the need for a strong-armed QB, and the difficulty in finding players like the dual-threat TE. It's also easier for a safety to read a TE and recognize play-action from a quarters alignment.
With the deep threat slot receiver in run and shoot style spread concepts, an offense can take some of the best I-formation and spread tactics and fire them at a defense without having to find NFL-caliber talent. Safeties have to keep their eyes on split out slot receivers rather than in the backfield and defenses are fragmented and isolated, no longer able to so easily outnumber the run.