No two terms are bandied about more in football today than "spread" and "pro-style." From recruiting to Saturday commentary, they are ever-present. But the distinction between the two offensive systems are ill-defined and the concepts are often not explained or discussed. So it is worth asking – what is the difference?
Part of the confusion arises from the terms themselves. It often appears that pro-style is used to define any offense where the quarterback is under center and spread for a quarterback in the shotgun. But quarterback alignment is a tactic. Alternatively, the term spread is used for a running quarterback while 'pro style' is applied to a pass-first signal caller. But this is looking at the effect and not the cause.
The upshot is that the terms are both over and under fitted. For instance, "spread" is often used to describe both Urban Meyer's and Mike Leach's offenses. But Meyer's "spread to run" and Leach's Air Raid are very different in terms of philosophy, approach, and emphasis.
It is thus worth limiting the term spread to spread to run offenses. But that limitation still begs the question of what really separates a spread offense from a pro-style one.
A Common Ancestry
In some ways the similarity between the two are more important than their differences. They are both an outgrowth of the one-back offense that Don Coryell, Joe Gibbs, Dennis Erickson, and others developed in the late 70s and early 80s. It is the offensive system that most associate with 'modern' football. The offense can use four wide receivers, two tight ends, or even a blocking fullback, but the basic concept is the same. The offense is essentially a mix of the main tailback runs of inside zone, outside zone, power, and counter-trey with a conceptual passing game.
The style of offense is distinguished from series football such as the Wing-T, where plays begin looking identical to one another and involve a series of fakes. The one-back offense is predicated upon mini-series – individual base plays such as inside zone that are protected by constraint plays such as a play-action pass.
Unlike series football, this style of offense often relies upon the passing game, rather than faking, to prevent a defense from applying its numeric advantage (i.e. unblocked defenders) at the line of scrimmage. To take a step back, every defense has at least a plus one advantage against the offense. Since each side gets 11 players there will always be an unblocked defender – the ball carrier's counterpart. Against the one-back offense, defenses often have a second unblocked defender, that being the quarterback's counterpart once the quarterback hands off the football. As such, this offense must be able to effectively throw the football to control these two unblocked defenders. The passing game force a defense to play unblocked defenders at safety and/or controls another defender with the threat of a pass. As such, the one back system often uses four vertical threats at the line of scrimmage and is itself a 'spread' offense in the sense of counting receivers.
If this style of offense sounds familiar it should. It is the same basic framework used by pro-style teams today and has been run by every NFL team for the past 20 years. Nick Saban's Alabama lines up in some one-back variation. It bases its offense off inside zone, outside zone, power, and counter trey, with a play action and drop back pass game as a constraint. It is thus fair to say that "pro-style" equals the one-back offense.
So Whither the Spread?
The limitation of the one-back offense should be apparent to anyone that has been a fan of a bottom-dwelling NFL team. It puts a lot of pressure on a quarterback. A team must be able to throw the football, otherwise those unblocked defenders will crowd the line of scrimmage and the offense will quickly stall. And there are only so many guys that can stand in the pocket, read coverages, go through a 5-receiver progression across the field within 3-5 seconds, all while defenders are rushing you with a full head of steam.
Enter the spread-to-run. Offenses such as Urban Meyer or Chip Kelly's are still conceptually the one-back offense. Their offenses use the same base plays and constraint approach.
The spread's benefit, however, is that it is an additional method to constrain the defense's unblocked defenders beyond reliance upon the passing game. It does so by forcing the defense to also account for the quarterback as a run threat, thereby reducing the defense's numeric advantage by one. As Meyer states, he turned to the spread because he wanted to make it easier to run the one-back run plays. Meyer was in one-back and pro-style systems as an assistant coach, but the complexity of defenses (namely developing ways to put 8 and 9 men in the box while defending the pass) made it harder to move the football.
The spread provided a way to run the one-back offense but force a defense to play more honest by having to account for the quarterback in the run game. A spread team also runs inside zone, but then adds a quarterback read to the play to account for an unblocked defender.
Making the quarterback a run threat also allows the offense to use three and four wide receivers while forcing the defense to effectively defend an additional player in the box because of the quarterback threat. Everything in the spread offense is predicated upon forcing a defense to honor this more offensive-friendly numbers equation. Wide receiver screens, for instance, are used to prevent a defender who is ostensibly defending a wide receiver from cheating back into the box to regain the defense's numeric advantage.
Of course, no system is perfect. The spread offense also asks a lot of its quarterback, just in a slightly different manner. That player must be a threat to run or the offense's underpinnings falter. The bet for Meyer and others is that it is easier to find a quarterback that can run and make reads than one that must consistently beat a defense downfield with his arm alone.
Yin and Yang
The pro-style and spread to run offenses are thus more similar than different. They are predicated upon the same base principles and plays. The spread is best understood as an adaptation of the pro-style offense. It is an attempt to reduce the two-man numeric advantage a defense gets by forcing the defense account for the quarterback as a run threat. But the spread offensive coach's goal is in doing so is to make it easier to run the same pro-style plays.