Denver Broncos: The Return of Zone Blocking

     It's hard to argue with success. Fourteen years of the zone blocking system under Shanahan, eleven years with one back rushing for 1000+ yards, five years with one back rushing for 1500+ yards and one 2000+ yard rusher. It became an NFL truism that Denver could take any back, plug him into their zone blocking system and he would rush for one thousand yards or more.

     Many Denver fans were distressed when Josh McDaniels moved away from the zone blocking scheme in favor of a man-blocking scheme similar to the one used in New England. Those fans were further distressed when Denver's leading rusher logged 947 yards and 779 yards in the two years of the McDaniels experiment.

     There have been a number of voices raised in celebration over the indications that John Fox intends to restore the zone blocking system to the Broncos rushing attack. Visions of thousand yard rushers are springing to the forefront, much to many fans' delight.

     Yet, is a return to a zone blocking system all that is needed to restore Denver's reputation as a running back friendly team? After the jump, we'll take a look at this question.

     Zone blocking, in the simplest of terms, is a system used by offensive lines in which the blockers are assigned an area to block rather than being assigned a specific defender as is typical with man-blocking systems. It is a simple and effective scheme for creating running lanes for the running backs. Blockers are chosen based on their quickness, athleticism and discipline more than their overall physical size and strength. The goal of the zone blocking system is to force the defenders to move laterally along the line of scrimmage. It often entails two adjacent blockers throwing a combination block on a defensive lineman with one of the blockers then releasing to take on a linebacker at the second level; which blocker releases from the combination block is determined by the movement of the linebacker. For example, the play is moving to the right side of the offense. The right guard and right tackle combo block the defensive end on their side while watching the outside linebacker. If the linebacker moves to the inside of the defensive end, the right guard would release to pick him up, but if the linebacker moves to the outside of the defensive end, the right tackle would release to pick him up.

     This scheme is in contrast to man-blocking (also often referred to as gap-blocking and power-blocking) in which blockers are assigned a specific defender to block, with the goal being to drive the defender backwards off the line of scrimmage and out of specific gaps in the offensive line. This is a more complicated system to master, since the blocking assignments will change according to the pre-snap movement of the defenders. Physical size and strength, as well as quickness off the ball are the key characteristics for this type of blocker.

     As an aside, Laurence Maroney was often criticized for "dancing" in the backfield rather than sprinting into the gaps. I've begun to wonder if this was as much due to the offensive line not being able to drive the defenders backwards and open the gaps as it was to his being a poor choice for a running back. If the man blocking system wasn't working, there would have been no gap for him to run through and the dancing may have been an attempt to find a new hole, or to wait for one to open up. Just an after the fact point of curiosity.

     Zone blockers typically have a priority list of defenders to block: First assignment -- a defender lined up directly across the line from the blocker. Second assignment -- a defender near a gap who can be reached and blocked without assistance from another blocker. Third assignment -- a defender near a gap who can be reached and blocked with assistance from another blocker.

     Zone blocking is also typically divided into three general zones: Inside Zone -- runs that are aimed inside the tackles; the running back aims for a spot near the inside leg of the offensive tackle, and can cut back behind the center. Outside Zone -- runs that are aimed just outside the tackles, with the running back having the opportunity to cut back behind the guards. Stretch Zone -- the running back aims for a point just inside the last offensive player along the line of scrimmage; blockers may try to drive the defenders back towards the center, and there will be little chance for the running back to cut back towards the middle of the field.

     Zone blocking uses a variety of techniques to make the system work. It is a system that frequently uses deception -- allowing rushers and blitzers to penetrate the line of scrimmage in areas that are unimportant to the flow of the play while the blockers in those areas move to the point of attack. Three keys to making zone blocking work include: the blockers remaining hip to hip during the initial portion of the play, the blockers keeping their shoulders square to the defenders, and the blockers keeping track of the linebacker on the play side of the defense.

     With zone blocking there are a some things to keep in mind: (1)Because the running back does not have a specific hole to aim at, the blockers must be adept at reading the movement of the defenders in order to know which blocker must sustain the first level block and which must release to attack a defender at the second level. (2)Blockers must be able to quickly identify which defenders are first level defenders and which are second level. The level of the defenders is not a function of the defender's position (i.e. lineman, linebacker, defensive back), but rather which defenders are lined up in a position to make an immediate play on the running back (a first level defender) and which are lined up in a position to follow the movement of the play but are not an immediate threat (a second level defender).

     The Shanahan years were a good time to be a rusher in Denver. During his fourteen years at the helm, running a zone blocking, one-cut running attack, the Broncos had running backs rush for over 1000 yards eleven times, five times Denver's running backs topped the 1500 yard mark, and one rusher topped the 2000 yard mark. The 1000+ rushers included: Terrell Davis (95, 96, 97, 98), Olandis Gary (99), Mike Anderson (00, 05), Clinton Portis (02, 03), Reuben Droughns (04) and Tatum Bell (06). Davis and Portis each topped 1500 yards in multiple seasons -- Davis (96, 97, 98), Portis (02, 03). Davis was Denver's 2000+ rusher in 1998.

     This impressive group of runners helped the Broncos land near the top of the league in rushing on more than one occasion. The table below shows Denver's rankings in Rushing Yards (RY), Rushing Touchdowns (RTD) and Rushing Yards Per Attempt (RY/A). The table also shows the Broncos' rankings in Passing Yards (PY), Passing Touchdowns (PTD), Passing Yards Per Attempt (PY/A), Fewest Defensive Yards Allowed (FDYA), Fewest Defensive Points Allowed (FDPA).

     It is interesting note that Denver ranked in the top five in the NFL in Rushing Yards nine times, and in the top five in Rushing Touchdowns seven times. It should also be noted that every time Denver ranked that high in rushing categories, they also ranked in the top 10 in one or more of the following categories: Passing Yards, Passing Touchdowns, Fewest Defensive Yards Allowed and/or Fewest Defensive Points Allowed. In addition, Denver ranked in the top 10 in Rushing Yards and/or Rushing Touchdowns twelve times. In every year but one (2007), the Broncos also ranked in the top 10 in one or more of the following categories: Passing Yards, Passing Touchdowns, Fewest Defensive Yards Allowed and/or Fewest Defensive Points Allowed. This would suggest that the team was able to excel in more than one area -- the essence of playing complementary football.

     The running backs of the Shanahan years were certainly strong runners. Yet, they owed a fair portion of their success to the offensive line behind which they ran. The strength of the offensive line is often portrayed as the zone blocking system which was used. In some circles, it became almost an adage that with Denver's zone blocking system, any back could come in and rush for a thousand yards. But there was more to it than that. The first of the two following tables shows Denver's running backs from 1995 to 2008 and the yards they accrued each season. The second table shows the offensive linemen behind whom they ran.

     What we see here is that there were fourteen starting running back slots. Those slots were filled by nine running backs: Davis (5), Gary (1), Anderson (2), Portis (2), Droughns (1), Bell (1), Young (1), and Hillis (1). Of those nine, seven topped one thousand yards in a season. There were certainly reasons behind the others not reaching that mark -- such as the injury plagued season of 2008 in which Broncos running backs seemed to be dropping like flies.

     We see an even greater stability in along the offensive line behind which the rushers were running. From 1995 to 2008, there were twenty-eight offensive tackle slots, twenty-eight offensive guard slots, and fourteen center slots. Denver during that same span used just eleven offensive tackles, eight offensive guards and four centers. In other words, the seventy offensive line slots during this period were filled by just twenty-two players:

Offensive Tackle -- Zimmerman (3), Thompson (2), Jones (3), Swayne (1), Lepsis (8), Teague (1), Salaam (2), Foster (3), Pears (2), Clady (1), Harris (1)
Offensive Guard -- Schlereth (6), Neil (7), Friedman (1), Herndon (1), Hamilton (5), Carlisle (2), Kuper (2), Holland (1)
Center - Nalen (11), Hamilton (1), Myers (1), Wiegmann (1)

     Stability along the offensive line -- a crucial component for a successful zone blocking scheme (or any other blocking scheme) -- was very evident during Shanahan's years. That stability translated into a group of blockers who were intimately aware of what their teammates were going to do on any given play. Add in fourteen years of Mike Shanahan designing the offensive game plan and calling the plays, and the Broncos had a recipe for success. It was not until the last two years -- when there was a significant turnover in the offensive line and a series of running back injuries -- that the Broncos began to struggle in the running game. It was also during this period that the defense began to fall in the rankings in nearly every defensive category, which meant that the Broncos were not afforded the luxury of running the ball as much.

     The stability of the line along with the success of the running backs, and the often high rankings of the passing game leaves a curiosity as to what degree Shanahan's play calling and the effective execution of his plays were also responsible for the success of the running game. Unfortunately, that question is beyond the scope of this article.

     When researching this article, I found six teams often mentioned as using zone blocking as their primary blocking scheme in 2010. Those teams were: Washington, Indianapolis, Oakland, Houston, Green Bay and Carolina. The following table shows each team's rankings in Rushing Yards, Yards/Attempt, Rushing Touchdowns, First Downs, 20+ yard Rushing Plays and 40+ yard Rushing Plays. I have also included Denver's 2010 (non-zone blocking) rankings for comparison.

     It can be seen that in some instances other teams were very successful using a zone blocking scheme, while others struggled. The rankings run the gamut from very good to pretty poor:

     It should be noted that the Broncos (without the benefit of a zone blocking scheme) ranked ahead of Washington and Indianapolis in Yards, ahead of Indianapolis and Green Bay in Yards per Attempt, and ahead of Washington, Green Bay and Carolina in Touchdowns. Now, certainly, it should also be noted that the overall offensive philosophies and defensive execution of each of the zone blocking teams played a role in their rushing rankings. What appears to be the case with these teams is that the scheme was only as good as the personnel, coaching, play-calling and complementary play of the rest of the team. Thus in some cases, the rushing attack looked very solid while in others it was below the league average.

     Zone Blocking may well in deed be a salve that can heal many of the Broncos' rushing woes, but we would be wise to watch its implementation carefully and with a bit of wariness. John Fox will have to assemble the right coaches and players for the offensive line and effective one-cut backs for the rushers. Mike McCoy will have to create and call a game plan that uses the correct rushing play at the most opportune time. The running backs and offensive linemen will need to remain healthy throughout the offseason and the preseason in order to gain the most out of their preparation for the 2011 season. The defense will need to rise up so that the offense spends less time playing from behind. If all of these things come together, we could very well see another thousand yard rusher in Denver very soon. If they don't all come together . . . well, let's stay positive and believe that they will.