It gets said a lot that there's rarely anything really new in football. Every strategy or tactic has been done before in some form or fashion, and we're all just finding new ways, or twists on old concepts. Air-Raid passing teams use pass plays popularized by LaVelle Edwards at BYU in the 70s and 80s. Most spread running games uses concepts and theories that worked for the single wing, wing-T and of course, various option offenses.
So when myself and other pundits talk about the whole "spread vs. pro-style" distinction as largely arbitrary, at least in terms of how they're commonly used, it always comes back to this central tenant that has defined offensive strategy in this game ever since the flying wedge was outlawed in early days of the 20th century: an attempt to give a team a numbers advantage in an 11-on-11 game.
For the defense, typically, there's an advantage versus the run, because once the quarterback hands the football off, that's it. He's out of the play. He's not responsible for blocking anybody, and the 11 on defense now only have to contend with the other nine blocking and the ball carrier. Obviously, the threat of the pass is what the offense is counting on to force the defense to keep a safety man deep. But that's still more defenders than the man with the ball has blocking for him.
This is where tactics like misdirection and moving blockers around come into play. You give the defense a look designed to draw him in in one side of the field, while the ball and the blockers move somewhere where, if the play works, there are now fewer men to contend with. Pulling, trapping and scooping helped lead to the creation of most of what we think of as the classic running plays like power, counter, etc...
Using plays that are designed to make defenders hesitate, or think that they're running free to set up a surprise block, eventually led to tactics that involved just leaving players unblocked all together. When a play is run away from them, backside defenders near the line of scrimmage typically have containment responsibilities - their job is to "stay home" so to speak. Pursue, but make sure that they're in position should the ball suddenly come back their way, either through a reverse hand-off or a particularly ballsy running back cut. The contain player will typically loop somewhat wide first, and then run to the ball, as opposing to immediately crashing down the line of scrimmage.
One of the easiest ways to make sure that player stays occupied is to have the quarterback execute a bootleg off of the hand-off.
Notice how the designated contain guy is unblocked, leaving seven blockers on seven remaining defenders near the line.
Simple. The QB rolls out away from the play, generally faking as though he has the ball. If the contain man is doing his job, he'll make sure he runs right to him and keeps him from getting by. This inevitably led the quarterbacks actually keeping the ball for play-action passes or other designed runs that we've all seen before.
So what's this got to do with the spread offense?
Bootlegs are a staple of zone-blocking schemes -- Mike Shannahan's Denver Broncos playbooks had one off of virtually every run they had. And due to its ease of installation and tendency to favor lighter, smaller offensive linemen, zone-blocked plays became more and more common among the teams that favored shotgun-heavy offenses such as the old Mouse Davis Run & Shoot.
One of these coaches was a man named Rich Rodriguez, then the head coach at Glenville State University in West Virginia. After installing the run & shoot and finding that his quarterback saw the field much better staying in the shotgun as often as possible, Rodriguez had another revelation during an accident in practice in 1991 (outlined in Tim Layden's "Blood, Sweat and Chalk," which is a must-read if you have any interest in football strategy or the game's history - we've discussed it often here):
One afternoon (Glenville starting QB Jed) Drenning bobbled a snap on one of these zone-blocked running plays. Unable to get the hand-off delivered to the running back, Drenning tucked the ball himself and saw the backside defensive end crashing down the line of scrimmage to tackle the running back-who, in fact, did not have the ball but was behaving as if he did-from behind. On a broken play the quarterback customarily follows the running back into the assigned hole and tries to salvage yardage. But Drenning, seeing the end closing, instead ran wide into the area vacated by the end. "It was just an instantaneous reaction thing," says Drenning.
After the whistle, Rodriguez casually asked Drenning, "Why did you do that?"
"Do what?" said Drenning.
"Why did you run that way?" Rodriguez said.
"The end end pinched," said Drenning.
And thus was the birth of what we now know as the single defining running play of the spread offense: the zone read.
The action is the same for the quarterback out of the shotgun on a zone-handoff, but by accident, Rodriguez and Drenning had found a way to make something old, new again. They just added the "read" element of the Texas Wishbone to the Run & Shoot. And it's why today we see every quarterback run out a zone-read keep in spread offenses, regardless of whether he has the ball or not. I don't care if it's Dak Prescott or 240-pound Molasses McLedfoot, the quarterback will execute that fake as if he's got the ball to give his team a blocking advantage on the playside. Just like the bootleg. In fact, more often than not a lot of runs that look like a typical zone-read, especially in the NFL, are often straight handoffs (the Seattle Seahawks tend to let Russell Wilson keep only late in games after showing the "give" look a number of times) -- because having a quarterback that can be a dangerous runner is usually enough to hold that backside end.
And just like the bootleg, smart coordinators continue to find ways to incorporate the passing game, either with straight play-action passes or packaged option plays that allow the quarterback to give it to the back, keep it himself or throw a bubble screen or other short pass, based on a second-level defender (allowing the offense to sometimes freeze two defenders and get even more of an advantage in the run game).
It all just goes back to what I've been trying to explain about offenses in football. They're not as divergent as you might think, when it comes to "spread" or "pro-style." Just like with quarterbacks, we're not talking about either/or. Two different languages, so to speak. Football is always just football. And it's always about finding a way to get the extra man.