Donald David "Don" Coryell is not typically lumped together with the likes of Vince Lombardi, Bill Walsh or Don Shula as one of the greatest pro football coaches of all time, but his innovations have been just about as wide-reaching and influential as any of the greats in pro football history. Coryell is the namesake behind the legendary "Air Coryell" offense, whose distinctive tenets and philosophies are embedded, in one way or another, into every team's playbook in today's NFL.

Coryell first made a name for himself at San Diego State University from 1961-72, where he led his team to a 104-19-2 record using a then-rare pass-heavy offense. He amassed three undefeated seasons and contended with some of the biggest-name schools at the time, which propelled the Aztecs into Division I football and into the national conversation. Among his assistants at SDSU at the time were John Madden and Joe Gibbs (um, holy frickin' crap).

Coach Coryell had studied the schemes and philosophies of TCU's Dutch Meyer, who penned Spread Formation Football in 1952, as well as Rams and Chargers coach Sid Gillman, who Al Davis called "the father of modern-day passing" for his innovations in the downfield vertical attack. These were doctrines that Coryell had adopted with gusto, then refined into his own system at SDSU.

Coryell, paradoxically, was a heavy proponent of the I-formation earlier in his career, but changed his mind suddenly and never went back.

"When I first came [to San Diego State] in 1961," Joe Gibbs told Tom Layden for Blood, Sweat and Chalk, "Don was a killer running coach. I-formation, power running. Just killer. But then it's amazing the transition that took place. Don switched to throwing it like mad, and he was very creative. He was not afraid to try anything."

"I just decided, hell, you can't just go out and run the ball against better teams," Coryell said. "You've got to mix it up. You've got to throw the damn ball if you're going to beat better teams."

"We could only recruit a limited number of runners and linemen against schools like USC and UCLA," he recalled.

"And there were a lot of kids in Southern California passing and catching the ball. There seemed to be a deeper supply of quarterbacks and receivers. And the passing game was also open to some new ideas. Finally we decided it's crazy that we can win games by throwing the ball without the best personnel. So we threw the hell out of the ball and won some games. When we started doing that, we were like 55-5-1."

He expanded and evolved Gillman's philosophy, and his innovations (and guts) would help shape the pass-heavy offense that makes up the paradigm in the modern NFL.

Coryell is credited with a laundry list of innovations. He was the architect behind the one-back formation, developed the "joker" tight end, pioneered the use of option routes, devised the flood route combination, conceived the numbered route tree/play-call lexicon, and was integral in the advancement of the use of pre-snap motion and running back screens.

As a corollary, Coryell's innovations changed the way teams played defense (more nickel and dime), how they scouted players and what they prioritized in their players (speed, speed, speed and coverage ability).

During the late 1970s, he brought that philosophy to the St. Louis Cardinals and rejuvenated a stagnant franchise.

His offenses in San Diego in the early 1980s, though, really opened everyone's eyes with his departure from the "smashmouth" run-oriented offense that ruled the day.

"He was way ahead of everyone in terms of innovation. There was this unspoken set of rules that you played by on offense. And everyone was running generally the same kind of plays. The formations were the same. The concepts were the same. Coryell changed all that. People immediately said, 'You can't do that.' Well, you can do that, and he did it. His whole approach to the game was different. He was going to beat you with the ball at any time. He had this aggressive mind-set. He was always attacking the defense, never going into this conservative mode where you try to win through attrition. And that's where football was at that time in history. Now, 40 years later, you're seeing the second and third generations of coaches running Coryell's system." - Mike Martz, "Blood, Sweat and Chalk"

With Coryell's system, his Chargers were the sexiest team in the NFL from the end of the 1970s through the first half of the 1980s. They led the NFL in passing yards five straight years -- 1979 to 1983 -- and then again in 1985. They led the league in total yards from 1980 to 1983 and again in 1985. The 1979 Chargers were the first AFC West champions to run more pass plays (541) than rushing plays (481). Can you imagine this? Almost no teams run more than they pass anymore (and none did in 2013).

The Air Coryell

As Layden posits in Blood, Sweat and Chalk, Coryell's "offensive system is based on three elements: simplicity, spacing and timing."

Whereas Bill Walsh's West Coast offense looked/looks to spread the defense horizontally, the Air Coryell offense unapologetically looks to spread the defense vertically as well. The idea is to make the defense cover the entire field, and three- or four-wide receiver sets became commonplace. Of course, a power run game was not forsaken, and it was used as another weapon when teams backed up, spread out and got smaller in response to the passing attack.

Dan Fouts, Getty Images Dan Fouts, Getty Images

Of course, the main thing was to throw the ball deep. And they did that a lot.

"The first thing in our offense was always the bomb," said Hall of Famer Dan Fouts in Ron Jaworski's The Games That Changed the Game. "It was built into almost every pass play, where the quarterback initially looks for that chance to hit the big one. And I think if you start with that premise and then work your way back toward the line of scrimmage, that's the Air Coryell offense."

According to Layden, Coryell aimed to instill two rules with his quarterbacks:

1) "Never pass up an open receiver. If he's there, stop reading and throw it to him."

2) "Never, ever worry about an incompletion. You don't give a damn about incompletions. Just go back and get it the next time."

With more receivers releasing into routes, the natural disadvantage is that it leaves your quarterback in a less protected position. Thus, Coryell's quarterbacks were taught to get the ball out quickly -- mostly in three- or five-step drops -- but they also had to be tough sons of bitches. Dan Fouts, and later Troy Aikman and Kurt Warner, all proved they had the ability to stand tall in the face of pressure, stare down the gun barrel and let loose with a dart right as they were getting hit.

Schematic Legacy

Without getting too into Don Coryell's actual playbook, here are a handful of revealing pages from it:

The one-back offense

Prior to Air Coryell, the "pro set" was the default formation/personnel in the NFL. This involved two receivers, one tight end and two running backs, typically in a split formation behind the quarterback under center. With Coryell's emphasis on the pass, he swapped out one of those backs for a "move tight end" -- Hall of Famer Kellen Winslow -- and kept another "blocking" tight end inline to protect.

The pass-heavy offense

This is a staple of the modern game -- "it's a passing league" -- and while Coryell wasn't the first to throw the ball deep, he was a pioneer in the strategy to pass the ball more than running it.

Charlie Joiner reaches for a pass. Getty Images

The heavy use of motion

The 1978 passing of the "Mel Blount Rule" helped Coryell take his San Diego State offense and supercharge it for the pro game. The rule change gave defenders only a 5-yard cushion to jam and press a receiver (instead of free rein all the way downfield), which helped to open up the deep passing game greatly.

"It was built into almost every pass play, where the quarterback initially looks for that chance to hit the big one."

"Those liberalized 1978 rules created the perfect climate," says Ron Jaworski in The Games That Changed the Game, "in which to implement previously unseen formation shifts and men in motion. If defenders were allowed contact only near the line of scrimmage, why not have receivers moving prior to the snap, where they'd be almost impossible to jam? And why limit this to wideouts? Why not running backs or the tight end as well?"

Coryell moved players all around the formation -- tight ends out, wide receivers in, running backs all over.

"A defense had to account for all that shifting," recalls Al Saunders in The Games That Changed the Game. "Winslow shifting from backfield to tight end, backs in motion. Don wanted to get an advantage before the snap. Some teams did that with cadence or audibles. Don's movement created mismatches and confusion with the defense. When I first got to San Diego, I asked Ernie Zampese why they did so much shifting and movement. His reply was, 'Sometimes we just do it to do it.' When you shift or go in motion, that causes at least two checks by the defense. So what happens if someone doesn't hear the check or hears it incorrectly? Now he's out of position, or you have the wrong defender in place."

Increased effectiveness of pre-snap reads

Coryell and company didn't invent the quarterback's pre-snap review of the defensive formation, but his use of motion prior to snapping the ball made it much easier to distinguish man vs. zone.

"Motion produced another benefit," Jaws relates. "If a defensive back or linebacker rotated with the moving player during the pre-snap, this was a good indication that the defense was in man-to-man coverage. For a sharp quarterback like [Dan] Fouts, knowing this even before the play began was a tremendous advantage."

Nickel and dime defenses

The NFL tends to operate in cycles, and we're seeing this more and more recently: faster, smaller linebackers who can better cover tight ends in routes. This was one of the main trends on defense that followed the advent of Coryell's system, particularly with Winslow.

Nickel and dime defenses were used more often, more cornerbacks and coverage safeties were drafted, and defensive principles started changing to focus on defending the pass. Action leads to reaction.

Option routes

One reason that rookie and second-year receivers often have a difficult time adjusting to the NFL game is the frequent and wide use of option routes. Essentially, an option route (or its cousin, the sight adjustment) is a route that the wide receiver chooses based on the defensive positioning. In theory, option routes will always be open because they're designed to run away from the given coverage on a play. The tricky part of course is getting on the same page as your quarterback and making sure the ball is going to the spot you decide to run to.

In theory, option routes will always be open because they're designed to run away from the given coverage on a play.

"In [Coryell's] passing tree, you can give your receivers two or three different routes," explained former three-time All-Pro wide receiver John Jefferson in The Games That Changed the Game. "In San Diego, the coaches allowed us the freedom to change those routes, depending on the coverage. Dan [Fouts] pretty much knew when we were going to break those routes and when to release the ball. Sure enough, we'd be there. This made it difficult for defenses to shut us down. They might have the proper coverage to stop that first route, but when we changed it, we had them beat."

Move tight ends

Coryell turned to then-offensive coordinator Joe Gibbs and Winslow to develop the idea of using a tight end as a pass-catcher, and Winslow was the first in what's become a growing group of big, insanely athletic and versatile players at that position. As Al Saunders recollects in The Games That Changed the Game:

"You have to understand how tight ends were being used in the early 1980s. Their primary function was as a blocker, then to move out to the back side as part of the route and run a drag route. Or they'd run hooks inside, or get open in the flat. That was it. They were all big guys, 'tackles' who could catch the football. Plus, outside linebackers could still grab a guy and smack him around trying to defend the run." It pained offensive coordinator Joe Gibbs to see Winslow's talent being held back by the traditional limits of the position. "When we lined him up at the standard tight end spot and he went to release, he got pounded by the outside linebacker in a 4-3 or the inside linebacker in a 3-4," he recalled. "He had a tough time getting off clean, and we felt we had to do something. So Ernie, Don, our O-line coach, Jim Hanifan, and I said to ourselves, 'Maybe the thing to do is take him off that line of scrimmage and start moving him all over the place.'"

Hence, motion.

Said Jaws, "Coryell and Zampese set Winslow up anywhere on the field. They put him in motion where he couldn't be jammed. They'd line him up in the slot or out wide against some unfortunate 5-11, 180-pound corner. How on earth can that guy defend a 6'5, 250-pound receiver who runs just as fast as he does? That's the classic mismatch that NFL coaches dream about, and in San Diego mismatches like this existed on every play."

As Winslow recollects, "We just started playing around with it. Our coaches saw something, and so I ended up in practice running the same routes as the wide receivers. I loved running those routes, the 'skinny post,' the 'deep post' -- and there weren't many guys then at 6'5, 245 who could run these traditional wideout routes. When you looked at the film, I ran the routes about as well as the wide receivers, although I was usually a step or two behind where they were."

Mike Powell, Getty Images

In Jaworski's words: "What Coryell and receivers coach Ernie Zampese did with Winslow was to take a player with extraordinary pass-catching ability and create positions in which he could be the primary receiver."

The use of the numbered route tree in play-call lexicon

You've probably seen a route tree, and may have wondered about the numbers assigned to each route. Well, Coryell thought it up.

"The foundation," writes Layden in Blood, Sweat and Chalk, "is based on this: Routes for the outside receivers in a formation (typically designated the X and Z receivers) are assigned single digits, from 1 to 9; routes for an inside (or Y) receivers are assigned multiples of 10, from 10 to 90). A basic pass play might begin with the number 837, which means the outside X receiver runs an 8 route, the inside Y receiver runs a 30, and the outside Z receiver runs a 7."

This simplified number system for play calls meant communication in the huddle was greatly improved and meant there was less chance for error or misunderstanding (as opposed to the extremely verbose and long-winded West Coast offense lingo). It was also a much more intuitive system, giving more easily memorizable clues to each player as to what his role would be.

"The way he arrived at the three-digit system and his way of calling the passing game was one of the more enlightening things that has ever been done in football," said Gibbs. "The system basically was: The higher the number, the deeper the route. Inside cuts were even-numbered, outside cuts were odd. That was easy to remember. On the first day Don coached a receiver, that guy could learn basic plays. The idea behind it was to give the quarterback a visual picture."

Zone flood

With Coryell's love for moving players around, the natural evolution was to stack three receivers on the same side. I'm not sure that I can confirm that he was the first to do it, but as former head coach Marty Schottenheimer posited, "putting three receivers on one side and flooding that area" probably originated from the Coryell offense.

Coaching tree

Coryell's coaching tree is absurdly illustrious and wildly successful. The list of assistants who worked with Coryell then took parts of his systems with them as coaches or coordinators includes John Madden, Joe Gibbs, Jim Hanifan, Ernie Zampese, Rod Dowhower, Al Saunders, Tom Bass and Jim L. Mora, among many others.

As you probably know, John Madden won his Super Bowl with the Raiders in 1976. Joe Gibbs took his modified Coryell system to Washington, where he won three Super Bowls; first in 1982, again in 1987 and once more in 1991.

Getty Images Getty Images

Ernie Zampese, who started out at San Diego State with Coryell, later taught the offense to Norv Turner. Turner took that offense, made some tweaks, which included a greater emphasis on sideline throws, and won two Super Bowls as offensive coordinator with the Dallas Cowboys in 1992 and '93. Zampese replaced Turner as offensive coordinator in Dallas when Turner got a head coaching gig in 1994, and was the offensive coordinator for the Cowboys when they won another Super Bowl in 1995.

Zampese would take Mike Martz -- who was obsessed with the Air Coryell offense -- under his wing to mentor him on the system, and Martz used those lessons to win the 1999 Super Bowl with the Rams' Greatest Show on Turf.

Other proponents of the Air Coryell system include Al Saunders, Cam Cameron, Tom Moore, Brian Schottenheimer and Jason Garrett, and both Bill Belichick and Sean Payton give credit to Coryell for the development of the move tight end, important in their offensive playbooks.

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Don Coryell never won a Super Bowl and is not in the Pro Football Hall of Fame, but his innovative approach will show up in every game this upcoming season.