Something's changing in the NFL. Over the past three seasons, the league has trended toward a pass-first game. The rules in place enable this change, and penalty enforcement over that time frame have placed emphasis on not hitting the quarterback or receiver.

Something else is going on. How are teams like San Francisco and Denver winning? Last February, right after the Super Bowl, I started to think about teams that "run first" in this current passing era. Here are my thoughts from February 10, 2011:

I'm super intrigued with a shift that I see from Bill Belichick. The Pats drafted two tight ends, traded Randy Moss, and ran more than in the past, and I wonder if he's onto something. With so many teams running spread formations and designing defenses to stop opposing spreads, I wonder what a good old fashioned smash mouth offense would do? The Jets and Steelers have had success when they've committed heavily to the run. Sometimes going counter-trend means being first, and that can mean success. Buffalo was early to the renewed 46 defense trend, and fielded great defenses under Jerry Gray. Buffalo stayed 3-4 when the entire league abandoned the defense, and were subsequently hard to play against - but then they were five years late to the Tampa 2 party, and it showed. Maybe going counter-trend has some merits.

After the jump, we'll examine the history or the league's offensive and defensive schemes and concepts, how Denver and San Francisco have gone back to the 1980s to find success, and how Buffalo is positioned moving forward.

Concept History. The modern era of offensive and defensive concepts and schemes are with the 1950s New York Giants. Jimmy Lee Howell coached the Giants in the NFL, with two future Hall of Fame coaches on his staff. Vince Lombardi coached the offense, and Tom Landry was the defensive coordinator.

Landry was the NFL's first master innovator. As an engineer, he was concerned with formations and angles, and invented the 4-3 defense. This defense put middle linebacker Sam Huff off the ball, instead of in the traditional 5-2 set where a nose guard covered the center. The 4-3 defense was dominant, and the defense is still used today as one of the base NFL concepts, one of eight concepts used today.

1960s. Most teams were running Lombardi's power offense and the 4-3 defense, with some teams, notably the Miami Dolphins, working with the 1940s version of the 3-4 defense. The first real innovation came late in the decade. Bill Walsh was coaching the offense in Cincinnati with head coach Paul Brown. The Bengals' offensive line could not sustain blocks, so Walsh turned to an older concept that Sid Gilman used: pass to run, and the quarterback threw to timed spots. Walsh ran the offense with shorter pass routes, keeping the quarterback in three- and five-step drops, limiting the defense's ability to get to the quarterback. Walsh required the quarterback to throw to a spot instead of a receiver. The horizontal timing offense became the first of the NFL's four major concepts to evolve.

Landry created the "flex" 4-3 defense, in which two of the four defensive linemen positioned themselves one yard off the line of scrimmage. Landry did this to allow his lineman to flow to the ball better, confuse offensive blocking angles, and free up the middle linebacker. The concept created the "Doomsday I" and Doomsday II" defenses, two of the most dominant defenses the NFL has ever seen. No one runs the defense today, though, because it was so complex that only Landry could effectively coach it.

1970s. The Walsh offense grew in complexity and became very successful, even when playing the Steelers, because the short passing game kept the defensive line off of the quarterback. The scheme continued to evolve under Walsh, and he took the scheme to San Francisco later in the decade. It worked against the Cowboys as well.

The Tampa 2 defense was born in Pittsburgh in the 1970s, owing its birth to Chuck Noll and Bud Carson. The defense was designed to have all four defensive linemen playing the pass first, and the run second en route to the quarterback. The three linebackers and all four defensive backs played zone, with the two safeties in a two-deep zone. Carson had Jack Lambert, the middle linebacker, drop into coverage. The scheme called for gang tackling and a high level of aggression. An immense amount of talent didn't hurt, either.

Interestingly, the Patriots became a hotbed of innovation in the 1970s. Chuck Fairbanks coached the team, and together with Hank Bullough, they developed the Bullough-Fairbanks 3-4 defense. While the 3-4 had been around for 30 years and used by NFL teams, the defense became the second of the NFL's eight defensive concepts in New England. In this version of the 3-4, the defensive linemen were responsible for two gaps, and the linebackers were responsible for making the plays. This change was a fundamental shift from how defenses were run at the time, where defensive linemen and the middle linebacker were the primary playmakers. Running this form of 3-4 also allowed the Patriots to acquire linemen that were expected to be gap-pluggers, and avoided trying to match the talent of the Cowboys and Steelers.

In concert with the new 3-4 defense, New England coaches Ray Perkins and Ron Erhardt modified the smash-mouth offenses of the decade and created the second of the NFL's four major concepts. The Erhardt-Perkins offense called for ball control by running first and throwing second, with many play-action passes. By running and completing high-percentage passes, the Patriots could keep the ball away from the other offense for most of the game.

Don Coryell became the NFL's third true innovator, after Landry and Walsh, when he designed the vertical timing passing game, the third of the NFL's offensive concepts. In the Coryell offense, receivers run to spots down the field, like Walsh's system, but the spots are much further down the field than that of Walsh's system. Coryell combined this deep passing game with the current power running game, and added the tight end as a major mid-range threat.

1980s. With three of the four major offensive systems working the the NFL, every NFC Super Bowl winner ran one of the systems, with the 1985 Bears as possibly the lone exception. San Francisco won four Super Bowls using Walsh's horizontal timing offense. The Giants used the Erhardt-Perkins scheme under Bill Parcells to win a Super Bowl. Washington won two Super Bowls with Joe Gibbs using a variation of the Coryell offense. Gibbs used three-receiver sets with one back, and one blocking tight end in place of a receiving tight end. There was a major reason for this change.

Defenses had to begin to account for the changes on offense, and they did in a big way. In 1981, the Giants selected Lawrence Taylor with the second overall pick in the draft. They placed him at right outside linebacker in their Bullough-Fairbanks 3-4, and watched Taylor's surreal blend of speed and power as he blitzed. Taylor's ability allowed the Giants to change their standard Bullough-Fairbanks defense into a hybrid, with Taylor's outside linebacker position evolving into a stand-up defensive end position. Some teams followed suit and called the position the "elephant." Taylor became the only player in the modern era who, based on his talent alone, compelled coaches to re-design a scheme. The 3-4 elephant concept is still in use today, though most teams use a one-gap version of the 3-4 in conjunction.

Buddy Ryan became the first defensive innovator since Landry. Ryan was convinced that the way to stop passing offenses was to get to the quarterback before the he could throw. Ryan's 46 defense was based on a 4-3, but called for three of the defensive linemen to align over the offenses' center and two guards. A defensive end would man the weak side, and both outside linebackers would line up on the strong side. The middle linebacker and the strong safety would play as interior linebackers. With linemen plugging up the middle, the Bears had five other rushers to hurl at quarterbacks. Combined with a large amount of Hall of Fame talent, the epic 1985 Bears defense paved the way to a Super Bowl win, and arguably the best single-season defensive performance in NFL history. The 46 is no longer used in the same form as that Bears team, but variations of the defense are still used today.

Dick LeBeau's "Blitzburgh" defense was invented in Cincinnati, where he coached the defensive backs and later took over as the defensive coordinator. His zone-blitz concept can be run out of any alignment, though he preferred a 3-4 defense. LeBeau's defense called for all players on the defense to be able to rush the passer or drop into coverage on passing downs. The scheme's strength was in confusing the offense, as who was blitzing and who was dropping into coverage changed from play to play. LeBeau had his coverage in zone to prevent big plays against the blitz.

Wade Phillips designed the seventh and second-to-last defensive concept late in the decade as the defensive coordinator for Denver. Phillips' 3-4 defense differed from the traditional Bullough-Fairbanks scheme in that the defensive linemen were one-gap penetrators, and one of the outside linebackers was always an elephant. The defense is still in use today, most successfully with Phillips in Houston.

The last of the four major offensive concepts used today, the sight adjustment concept, gained traction in the 1980s. The offense was always around, but it was used for the first time as a base offense. Mouse Davis took Glenn Ellison's high school offense to college in the 1970s. The design of the offense was to get the linebackers off the field, with the dominant NFL defenses in mind, by putting four receivers on the field all the time. More importantly, Davis had the receivers come to the line of scrimmage with multiple routes available to run, based on the defense. The receivers and the quarterback would adjust the routes based on what they saw, even after the ball was snapped. The offense first entered the NFL during the decade with the Houston Oilers. Conceptually, the sight adjustment offense was used by Jim Kelly and the Buffalo Bills late in the decade, who substituted a tight end, Keith McKeller, as a slotback and called the offense the K-Gun.

By the end of the 1980s, the basis of modern offensive football was complete, and seven of the eight defensive concepts were complete.

1990s. During the decade, all forms of offense and defense proliferated and evolved. The 1990 Giants won the Super Bowl with an Erhardt-Perkins offense and a 3-4 Bullough-Fairbanks elephant defense. Buffalo went to four Super Bowls using a sight adjustment offense. The Redskins, Cowboys, and Rams won Super Bowls using the Coryell vertical timing offense. San Francisco and Green Bay won Super Bowls using the Walsh offense, and Denver won two Super Bowls using a run-heavy Walsh offense. The Redskins, Cowboys, Broncos, and Packers used standard 4-3 defenses. The 1999 Rams won a Super Bowl using the Tampa 2, marking a resurgence of the old Steelers defensive concept.

Nearly every team used one of the four offensive concepts, and the concepts began to modify. Mike Shanahan ran the horizontal timing offense, but emphasized zone blocking and power running to set up West Coast passing. The Cowboys used Coryell's system with the tight end as a big part of the passing game. The Redskins and Rams hardly used their tight end at all, except to block.

The 4-3 became the defense of choice during the decade. Most teams still ran Landry's 4-3, though the Cowboys ran the scheme with more athletic players. The Tampa 2 became more and more prevalent, and Ryan and his students still ran the 46 defense. By the end of the decade, only two teams ran a 3-4: Pittsburgh and their zone-blitz, and Buffalo and their one-gap system.

2000s. Jim Bates finished defensive concepts with his version of the 4-3. In the Bates defense, the 4-3 set was similar to the Tampa 2. The exception was that both defensive tackles were large, two-gap nose tackle types, instead of penetrators. This allowed the defensive ends to rush the quarterback without fear of inside runs, and the linebackers behind the two tackles could be small in order to flow to the ball carrier. He used his concept in Miami with Jason Taylor and Zach Thomas to build some very good defenses.

The 46 resurfaced in a modified form, with only one linebacker on the strong side of the offense, which balanced the defense and allowed it to be used as an every-down defense. The Ravens, Giants and Saints won Super Bowls using the modified form of the 46. The Tampa 2 was used by a Super Bowl winner for the second and third times in Tampa Bay and Indianapolis. Pittsburgh won two Super Bowls with their zone blitz defense, and the Patriots used a standard Bullough-Fairbanks as their base defense during the decade.

Indianapolis became the first team to use a sight adjustment offense as their base scheme to win the Super Bowl. The spread formation became prevalent in all offenses. Jon Gruden ran his horizontal timing system from the spread, and Indianapolis ran the majority of its offense from the spread. Even New England, a team rooted in Erhardt-Perkins ball control, decided to run a spread passing attack that featured high-percentage short passing to control the ball.

Defensively, teams trended back to the 3-4 and away from Landry's base 4-3. The Tampa 2 became very popular by the middle of the decade, and flamed out later in the decade. More often, teams mixed defensive schemes into a hybrid scheme. Baltimore currently runs a mix of 4-3 and 3-4 personnel and switches between a 3-4, 4-3 and 46.

Offenses did the same sort of mixing. By the time that the Saints won the Super Bowl, both participants, Indianapolis and New Orleans, had base schemes but ran some of every form of offense. The Packers are based as a West Coast, horizontal timing offense, but use plays and concepts from each scheme. Most importantly, teams gravitated to high-octane passing games.

What's Next? NFL fans have witnessed teams use 4-3 defenses in the 1970s, 3-4 defenses in the 1980s, back to the 4-3 in the 1990s, and back to the 3-4 in the 2000s. Offenses were run-first in the 1970s and a mix of passing attacks and ground attacks in the 1980s, though passing attacks have become more and more important as time goes on.

Belichick has been a 3-4 advocate for over two decades, winning five Super Bowls using the set. What could make him jump so quickly to a 4-3? And why would he ditch his spread passing attack, and his best deep threat, just three years after going 18-1 and losing in the Super Bowl?

Over time, the 4-3 has been a better scheme to stop running attacks, and the 3-4, with its built-in complexity, has been a better pass defense. Currently, many of the teams are operating passing offenses and 3-4 defenses. In the 2010 playoffs, all the AFC teams except Indianapolis ran 3-4 defenses, and only the Jets and the Chiefs featured their run game. In the NFC, only the Packers ran a 3-4, but except for the Falcons, every NFC offense was a pass-first offense. This season, 13 teams play a 3-4, eight play a 4-3, six play a Tampa 2, and five play a 46. Offensively, though each team is mixed, 10 teams play Erhardt-Perkins as their base concept, 12 play a Coryell vertical timing scheme, eight play Walsh's horizontal timing offense, and two play sight adjustment. Two-thirds of the league runs a pass-heavy scheme, and teams are shifting to 3-4 alignments to slow them down.

Uniquely, the Jets, 49ers and Broncos have gone decidedly counter-trend. The Jets ran the ball to consecutive AFC championship games. San Francisco has run the ball more than it has passed, and has run mostly traditional sets. Jim Harbaugh's power offense uses three tight ends just as much as it uses the spread formation. All three teams play very good defense.

An interesting comparison is looking at the 2011 Broncos and the 1986 and 1990 Giants. While many fans and the media focus on Tim Tebow, he's not the reason they are winning. Those Giants teams in mention ran the ball and played great defense. Similarly, Denver's running game and defense is winning games for them.

In 25 regular season wins, those two Giants Super Bowl teams topped 30 points only four times.The 1986 Giants ran 558 times and passed 472 times, even with Phil Simms at quarterback. The 1990 Giants ran 541 times and passed 398 times, mostly with Simms, partially with Jeff Hostetler. The 1986 Giants ran the ball 54 percent of the time. The 1990 Giants ran the ball 58 percent of the time. The 2011 Broncos, with Kyle Orton at quarterback, passed 60 percent of the time. The Tebow-led Broncos are running 62 percent of the time. All three teams don't make mistakes, rarely score over 30 points, and keep games close so the defense is a factor.

I argue that the 49ers and Broncos are winning by going counter-trend. In an era where defenses are designed to stop the pass, both teams are running the ball and possessing the football. This style minimizes possessions for the opposition, and maximizes the effect of turnovers. With most teams passing, both the Broncos and the 49ers have the pass rushers to force some of those turnovers. This formula is exactly how the 1990 Giants beat the high-octane Bills, and how the 2001 Patriots beat the Rams.

League Summary. The league is trending back toward possession football and the run game. It won't change overnight, but the change is coming. As power football came back into style in the mid-1980s, passing teams like the 49ers and Chargers were still very successful. The current Packers and Saints won't lose effectiveness, but teams may choose to build their teams differently, as acquiring talent to play power ball is easier than trying to acquire an elite franchise quarterback. It wouldn't surprise me at all to see the Broncos defeat the Packers or the Saints in the Super Bowl using the exact same philosophy that Belichick used to beat the Bills in 1990 and the Rams in 2001.

The spread option isn't going to catch on in the NFL. There's a reason that the option hasn't been an NFL offense for fifty years - it doesn't work when teams game plan against it. Denver needed miracle comebacks to win against average-to-poor teams using the offense, and in the only two games that they played a playoff team, they got blown out. Only one of the 12 NFL concepts currently in use came about because of a player - the 3-4 elephant with Lawrence Taylor. Greats like Jerry Rice and Reggie White fit into schemes, and so will Tebow. As he becomes a better passer, the spread-option will go the way of the Wildcat - a situational play.

Buffalo Bills. Buddy Nix built the Bills from the football out. In his first two off-seasons, Nix drafted or signed two defensive tackles, two 3-4 ends, and four inside linebackers. As those young players improve and Kyle Williams gets healthy, Buffalo will be well-built to stop running attacks. Nix has also built a large offensive line that two runners - Fred Jackson and C.J. Spiller - have excelled running behind. Chan Gailey is a traditional Erhardt-Perkins coach, and Buffalo was among the league's best running teams before Jackson was injured. Buffalo may also be toying with the idea of letting Dave Wannstedt, a 4-3 coach, take over as defensive coordinator. Regardless, Buffalo is running a hybrid defense that can morph between a 3-4 and 4-3.

Buffalo is well positioned as the league changes. In the late 1980s, Buffalo went to the pass when the league was going run. In the middle of the last decade, Buffalo went away from a 46 style blitzing defense to a Tampa 2, only to be crushed by passing offenses that had figured out the weaknesses of the scheme. Buffalo now has a head coach with ball-control roots, a good ground game, and a defense whose future on the interior looks good. For once, Buffalo may catch a break and be ready as the league takes a turn.