It all starts in the trenches, they say.

Super Bowl XLVIII, still fresh in our memories, featured two teams seemingly on opposite sides of the spectrum when it comes to offensive philosophies. On one hand, you had the record-breaking, prolifically high-volume Denver Broncos pass offense, and on the other, you had the smash-mouth, methodically low-volume Seattle Seahawks unit.

However, at the absolute core of both schemes, integral to their functionality -- if we're really starting in the trenches -- you could find Zone Blocking Scheme principles, developed by a man named Alex Gibbs.

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Alex Gibbs did not invent the zone blocking scheme. Its origins go way back to the post-WWII era of football, if not further, and it was popularized in the NFL in Cincinnati in the late 1980s. However, Gibbs' version took the NFL by storm in the mid-to-late '90s, and his coaching tree or sphere of influence is still wide reaching today, as evidenced by the Super Bowl XLVIII matchup. Gibbs, after all, is still presently a consultant with the Broncos.

The late 1990s: The heyday of the Zone Blocking Scheme

Now, to take you through the history of the development, who better than Gibbs himself to lay it all out? As Gibbs explained in a coaching clinic:

"The wide zone is a catchy term. It started in my world with Coach [Jim] McNally and the Cincinnati Bengals. He had a big running back by the name of Ickey Woods. That was the first exposure I had with this play. I studied the play and knew I wanted to get it into a system. "I had a chance to study under Joe Gibbs and Joe Bugel, who were running what they called the wide gap. They were experimenting with the play. However, John Riggins and some of those other guys could not get out wide enough for them to run it effectively. Nevertheless, they were trying to find a way to run this play."

The seed is planted:

"When I went to the San Diego Chargers, we started running the play. I saw it emerge there with a couple of great young backs we had on the team and that time. I had it in the back of my head that if I could ever get into a position to dictate the source, I would run this play. When I say dictate the source, I mean to influence the person in charge of the running game, I was going to feature this play. "At San Diego, I had to incorporate the play with about eight other offenses the coordinators wanted me to teach."

Gibbs coached with the Chargers from 1990-91, and is referring to Marion Butts and Rod Bernstine, presumably. The Chargers were among the league leaders in rushing in 1990, and in '91 they led the NFL with 4.8 yards per carry and finished second with 2,248 rushing yards -- behind only Thurman Thomas and the Bills' potent ground attack.

"I had it in the back of my head that if I could ever get into a position to dictate ... I was going to feature this play." -Gibbs

Gibbs continues:

"I went to a couple of other jobs and they did not want to make this system the feature play. Finally, I went to Denver with a friend who wanted me to put in that system."

The friend Gibbs is referencing is Mike Shanahan, and the year was 1995. Gibbs became the assistant head coach of the Broncos, in charge of the offensive line, and Shanahan had him implement the zone blocking scheme that he'd been ruminating on for years, to couple with the Shanahan/49er West Coast Passing offense. It would be a marriage of schemes that would eventually propel the Broncos -- with an aging but wily John Elway at the helm and out-of-nowhere Terrell Davis taking handoffs -- to the elite echelon in the NFL, punctuated by two straight Super Bowl victories in both 1997 and 1998.

At the core of the Broncos' success was the Gibbs Zone Blocking Scheme, which asked its running backs to run a very specific way and utilized undersized but athletic offensive linemen, all working as one.

As Tim Layden wrote in "Blood, Sweat, and Chalk," "In a four-year period starting in 1995 and culminating in back-to-back Super Bowl victories to end the '97 and '98 seasons, Terrell Davis ran for 6,413 yards. Eight different offensive linemen started at least 14 games for the Broncos; all of them weighed less than 300 pounds. They were quick and athletic, and if their cut blocking rankled opponents who deemed it dangerous or career-threatening, it was also well within the rules."

The basics of the zone blocking scheme:

The zone blocking scheme can be distilled down to two plays: the inside, or tight zone run, and the outside, or wide zone run. I'll focus on the wide zone, because that's more iconic to what Gibbs built the Broncos' offense on. The very basic explanation of the wide zone is that rather than attacking downfield, offensive linemen are taught to step laterally at the snap of the football, occupying their defenders, not necessarily blowing them up.

Offensive linemen go to the line and ask themselves (in extremely basic terms, though there are a multitude of "rules" involved): "Am I covered, or uncovered?" Covered would mean that there is a defensive player lined up across from him, and uncovered would mean he does not have a defensive lineman in his face.

"We coach the running back to take what the defense gives and read the defenders from the outside to the inside." -Gibbs

If that offensive lineman is covered, he just blocks the guy in front of him. If he's uncovered, he doubles up with the teammate next to him (to the play-side) to help him block his guy. Once he feels his teammate has his opponent under control, he breaks off and heads downfield to block. On the backside of the play, you cut block.

Watch the footwork and technique here by the offensive line, taken from some coaching tape of the Broncos from that mid-to-late 1990s team. It's intentionally choppy, as Gibbs looks to show what each player is meant to do:

Above, you can see:

1) The right tackle and right guard double up on a defensive end. Once that right guard feels his teammate is good to go, he peels off and heads up to take on the closing linebacker. He doesn't really take that linebacker out, but he occupies him enough for Terrell Davis to run past him. Even a moment is enough.

2) The center on this specific play does a great job of washing the nose tackle down the line.

3) The left guard and left tackle cut block on the backside. This is controversial, but still legal today.

4) The bootleg. The bootleg is a huge part of the ZBS, and as you can see above, Elway's boot holds the backside safety for a split second, which keeps him from crashing down on the run play to hit Davis near the line of scrimmage.

Says Gibbs:

"One of the big problems for the wide zone play is the chaser from the backside. The easiest way to control the chaser is to run the quarterback on keeper plays out of the backside. Offensive coordinators do not call enough bootlegs and nakeds to slow down the backside rush."

The basic overall idea is to get the defense flowing toward the sideline, and the running back then has a read to make, depending on which specific play is being run. If the defense is over-aggressive to the outside, the running back will cut it back upfield. If the defense is too worried about the inside cutback lane, the back can take the ball out to the edge. Combine with cut blocks and bootlegs to hold backside defenders. Simple.

Well. I say simple, but it's exceedingly precise. Gibbs has everything down to the footstep.

"We run zone wide and tight, and that is it. If you want to run something else, do not call me and ask for help." -Gibbs

From Alex Gibbs himself, transcribed from a coaching clinic:

"The quarterback puts the ball into the back's pocket and bursts out the other side on a naked action away from the play. He takes two quick steps in that action every time he runs the play. He has to make sure he does not bump the running back as he bursts away from the handoff."

The importance of the bootleg/;

"The quarterback gives the ball to the running back between the back's first and second step. The running back has one good step, and he is about to hit the ground with his second foot when the quarterback begins to seed the ball. On the third step, the runner has to make a decision. If the runner does not make the decision on the third step, you have the wrong running back for this offense."

Terrell Davis is the best-known Gibbs runner, but many other previously unheralded backs had success in this system, not because they were the best athlete or the most exceptional talent, but because they could hit their third footstep and make their cut decisively:

"We coach the running back to take what the defense gives and read the defenders from the outside to the inside."

Below, Gibbs shows what not to do, in his trademark (awesome) North Carolina drawl and not suitable for work or children language:

Says Gibbs:

"On the third step, the running back is either going downhill or taking the ball outside. The reason the decision is made on the third step is the timing of the blocks within the offensive line. On the third step, the offensive lineman make their push on the defenders. The push of the offensive line and the cut of the back must coincide."

"You beg teams to blitz you, because when you pop the seam, the back is in the secondary. That is how you lead the league in long runs." -Gibbs

Above, Davis hesitates and while there is suitable blocking up front (minus the detestable cut block by the right tackle), the play doesn't go far. A big part of Gibbs' system was eliminating double-cuts, improvisation, or attempted playmaking. He wanted running backs that would do what they were supposed to do, no matter what.

Gibbs:

"The back does not know where the cut will be until he gets his third step on the ground. He makes his decision on that step and commits to it. Whatever decision he makes, he lives with it. He does not dodge defenders or double cut with the ball. He takes what the picture says and gets the ball upfield and outside right away."

Example (in Gibbs parlance, "Had he chose inside, the big play would have been downhill"):





Gibbs was obsessed with the cut blocking on the backside -- it is one of the keys to the success of the play. If you get the defense flowing to the play-side, but have backside defenders pursuing down the line, there will be no cut back lane. Thus

"We entice our players with added points, which translate to added money in our league. We make charts, give T-shirts, and do anything we can think of to get people on the ground. We have a cut-block film each week of the cut blocks in the game. The head has to be over the front, but we want everything that moves behind the ball cut down."

In addition to that, receivers had to be blockers in his system. As Gibbs put it, "If the runner starts double cutting or bounces the play, he is coming to the sideline. If that wide receiver does not block the safety, he comes to the sideline. I think those are basic principles, and I try not to do it any other way."

Example:

Gibbs: "We don't block corners, we block safeties. We make corners tackle. They're as shitty as tacklers in our league as they are in yours."

These principles outlined above are all alive and well in many NFL offenses today, namely the Seahawks, Broncos, Texans, Redskins, Packers and Dolphins. The Ravens and Browns will feature the zone blocking scheme heavily in 2014.

Evolution, and Gibbs' coaching tree:

Gibbs and Shanahan parted ways in 2003 and the former ended up in Atlanta, where he coached or consulted for three seasons. He further developed the zone blocking scheme, but added in the extra component of the mobile quarterback (with Michael Vick). "During Gibbs' three seasons in Atlanta," as Chris Brown of Smart Football points out, "the Falcons led the NFL in rushing with more than 8,100 yards. Most impressively, the Falcons were the only team over that three-year period to average more than 5 yards per carry." Gibbs taught his system to then-Falcons assistant and current-Seattle coach Tom Cable, who in turn churned out his own version with the Raiders and currently the Seahawks.

The seeds were sewn there for several offenses of the present day that marry the zone blocking scheme with mobile quarterbacks and the read option, including the Redskins with Mike and Kyle Shanahan and Robert Griffin III, and the Seahawks, Tom Cable, and Russell Wilson. Undoubtedly, Kyle Shanahan will look to do this in Cleveland with Johnny Manziel.

Additionally, the offenses that the Packers Mike McCarthy and Dolphins (with Joe Philbin, who learned it from McCarthy) run with Aaron Rodgers and Ryan Tannehill, respectively, utilize the athleticism of the quarterback on bootlegs and rollouts. It's an evolving scheme. Gary Kubiak is now the coordinator in Baltimore and he'll implement what he built in Texas in his new offense.

Gibbs' philosophies change and evolve continually through Cable, Kubiak (who was Shanahan/Gibbs' offensive coordinator during the Super Bowl runs), McCarthy (who learned the ZBS from Gibbs in Kansas City), and Kyle Shanahan (who learned it from Gibbs and his dad), among others, but the core thought remains.

"In this system, whether it's Alex, myself, a couple other guys, we've never not had a good back," explained Cable recently. "I mean, we had a kid in Oakland, Justin Vargas, well they said ‘He can't play, he runs too high', all he did was run for like 1,180 and 1,200-something, so I mean, that ain't bad. So, whoever it is can go for 1,000-plus."

"In this system, whether it's Alex, myself, a couple other guys, we've never not had a [productive] back. Whoever it is can go for 1,000 yards." -Tom Cable

It's the system. It consistently produces results when run correctly. Alfred Morris, a sixth-round pick, in Washington. Arian Foster, an undrafted free agent in Houston. Marshawn Lynch, an afterthought and cast-off from Buffalo, in Seattle. Ultimately, it's about players buying into the system and running it how it's meant to be run. Lynch struggled initially when arriving in Seattle, but has since become one of the league's top backs.

Tom Cable: "We made a deal [shortly after he arrived in Seattle]: You have to do it the way I tell you to do it, I ask you to do it. And he's done it. So a lot of credit goes to him because he was willing to kind of maybe push his ego or push own beliefs, to some extent, aside and then embrace something new."

"Because," Cable went on, "this is a system that asks backs to do things a certain way. Once you get in and through the line of scrimmage, then do your thing. You can do all the craziness you want then. But you've got to do it this way from A to B. And he bought in from A to B. And after that, what you do from C on is you."

"We don't turn the ball around and hand it off and say go get em," Cable explains. "There are certain reads, there are certain beliefs in how we do things, and you have to understand the whole thing. This is not sandlot football. I think that's the great thing about our system. Since coming into the NFL in 2006, it's kinda always been at the top of the league in rushing and the backs we've had have been excited about being in it, and have fun with it. There's a long line of them now that have all been 1,000-plus-yard guys.

"It demands a certain discipline. It's not more complex [than other systems], and I'm not a rocket scientist so I know it's not all that [complex], but I know this: It does take a certain discipline to play in it, to run in it. If you're disciplined within the system, it will take care of you. That's what it does."

"I've always equated it to running a full-court press, in basketball," said former NFL lineman Seth Payne on the Chalk Talk radio program with Doug Farrar and Rob Rang. "You have to have guys that are really tough-nosed, grinder-type guys that can work together and have really good endurance. You end up with smaller offensive linemen, you get scrappy guys -- I hate that word, but it's true -- you get scrappy guys, receivers that can block downfield, and it's very effective. It's a real team concept."