Run Defense: Run Fits and Fitting the Puzzle Pieces Together

It's the Internet; I Really Don't Know What I'm Talking About

Well, this is my first post. I've been known to post replies that were overly complex, convoluted and long winded. Occasionally I've been asked to write a fan post. Eh, I'm usually just too darn lazy. But with the Niner's giving up a historic single game rushing record a couple weeks ago; I thought I'd look into it. So wouldn't you know it, my first post will be about something I don't know that much about and can't get into to too much detail. But hey, that's why we have the internet! To provide inaccurate or incorrect information; who knows, maybe I'll start writing football entries into Wikipedia.

There's an "I" in "Mistakes" But Not in "Blowout"

Generally speaking, when a team is consistently defeated in some aspect of the game, I suspect a schematic or tactical problem. I mean I can understand player breakdowns here and there. Some guys make mistakes are just flat out beat on some plays. But when you're run on for more than 200 yards more than one guy is messing up and that's when I started to thinking about run fits.

So what are run fits? It's sort of a complex answer and you'll hear different definitions that encompass gap assignments and run defense/gap schemes. But put simply it's how a defense defends a specific play through coordinated gap assignments and specific tactics. Hmm that sounded overly complex; basically you don't just want the defenders to go forward and attack the ball carrier you want them to have a good idea of where the ball carrier is going and where to funnel him.

Most of you here reading this probably know what gaps are.

Gaps & Techniques

Most think about defensive schemes in simple terms of one and two gap assignments. Well, defenses aren't static during a game so those gap assignments change as do the way the defensive linemen attack a blocker or gap. So next let's talk about gap assignments and run defensive schemes. A few years ago a poster named Ougadas (wish he still posted) wrote an excellent article about run defense Breaking Down the 49er Running Game Part 2 : Base Defense

Force & ContainFill & Spill

So basically he describes two basic run stopping schemes: Force & Contain and Fill & Spill. Put simply, the goal of Force & Contain is to funnel the ball carrier back towards the middle. Defensive players on the outside force the ball carrier back towards the middle of the formation and into the fill players in the middle. The goal of Fill & Spill is for the inside defensive players to push the ball carrier to the outside defensive players. The defensive linemen penetrate and push the ball carrier to the outside linebackers, safeties and corners. Classic 2 gapping 3-4 teams generally run a Force & Contain scheme. Most 4-3 teams run a Fill & Spill scheme. Those are the very basic two philosophies. Most defenses run far more complex schemes that often combine the two schemes. A couple of things not mentioned or expanded upon in this article alley "alley" players and force defensive back players. The alley player has responsibility for the area between the outside most fill player and the force player in case the ball carrier does not turn back from the force player. He is usually a defensive back. This will be important when we discuss the 49ers and their attempt to defend against Seattle's run game. Here's a diagram that includes the defensive backs and their roles.

Force & Alley Players

It's a Grand Defensive Plan....And God is Laughing

So here's the catch: YOU CAN FILL ALL YOUR ASSIGNED GAPS ON DEFENSE AND STILL GET BLOWN OUT AND RUN OVER. How is this possible? Well to most people a football gap looks like something like a hockey goal or smaller. But to a defensive lineman it's like defending a soccer goal. Football is a game of angles and on the line it's all about leverage and angles. What's of critical importance in defending a gap is what side of the gap you're attacking. The gap control scheme your defense is running determines how you attack your gap. If you're goal is to spill the runner out side the defensive lineman will attack the inside part of the gap. If the goal is to contain the runner, then the d-lineman will attack the outside part of the gap. The goal is to "flash some color" so the runner sees the penetration or clogged gap and goes towards the intended direction (or if you get lucky, make the tackle in the backfield). It's aiming for an inside or outside blocker's shoulders getting your hips on the inside or outside of that blocker's hips (which gives you angle and leverage advantage).

Hey! Where'd My Gap Go!

So those offensive linemen are big guys but they don't stand still and often don't just block what's in front of them. Offensive linemen pull and trap block. They down block (block the defender down from them not in front of them), reach/hook block ("reaching " for the outside shoulder of a defensive lineman and "hooking" him usually to seal the edge of a hole for the runner. While defensive linemen are targeting offensive linemen's shoulders and trying to gain the angle advantage, offensive linemen target the defensive linemen's shoulders to gain the advantage for their blocks.) We often think of 2 gap defensive linemen as reading and reacting and one gap defenders simply attacking their gap. But the truth is that both have to make some reads. It's a dance between the offensive and defensive linemen; the offensive lineman tries to make his proper block for the specific play and the defensive linemen try to control the gap according to the gap scheme and fit).

So when a guard pulls, the space he opens up makes two gaps one gap and the hole he runs to turns one gap into two gaps. The same for a lead blocking fullback. When a fullback goes through the hole suddenly one gap becomes two gaps. Linemen and linebackers need to know how to attack these new blockers and gaps; do they attack the inside or outside shoulder of the pulling guard or lead blocking fullback? Again, it depends on where you want to funnel the ball carrier. Push him back? Attack the outside shoulder. Push him out? Attack the inside shoulder.

It's a big moving jigsaw puzzle to find the right run fits. Defensive linemen have to readjust if they're supposed to attack a specific offensive lineman's shoulder to defend a gap and then the lineman pulls out and suddenly two gaps become one and you have to reach over to the next lineman's shoulder to protect the correct side of the gap. Inside linebackers often have to decide weather or not to fill vacated inside gaps or scrape and flow to the ball carrier in new gaps. Also, players need to adjust during the play. If the force player gets beaten to the outside, the alley player then has to become the force player and adjust his angle of pursuit to prevent the ball carrier from getting outside him.

I Love it When a Plan Comes Together

So how do the defensive linemen and linebackers know what to do? Well the first thing to do is to start with a plan. Most offenses have bread and butter plays. Plays they do well and run often. So defenses can plan to specifically stop them.

How can defenses tell what's coming at them? Linemen and linebackers look for keys. Linebackers have the luxury of watching from a distance and can watch for pulling linemen, down blocks etc. to determine what plays are developing. Defensive linemen have to be able to recognize pressure and movement by offensive linemen. If they can determine the kind of block coming at them then they can narrow down the offensive play and make the appropriate fits/adjustments. Defensive linemen can sense pressure and can recognize offensive linemen movement. Movement that begins with an offensive lineman's first step.

Offensive Lineman Dance Chart

I'm not saying that a defensive linemen will see an O-lineman's first step and think "it's a lead step, he's going for a down block". But he will get a sense of when that O-lineman steps sideways or back at an angle which way the block is coming or where the O-lineman may be going which may indicate what the play is.

Inside linebackers are the key components to the fits. Often inside linebackers must determine which gap to fill or to scrape and flow into newly created gaps. In a 3-4 scheme with 2 inside linebackers, usually it's the play side linebacker that takes on the lead blocker (fitting inside of him if he's spilling the ball carrier) and the backside linebacker that scrapes and fits sometimes right next to the play side backer (in his back pocket). But he has to determine if the gap that opens up inside on his side needs to be filled and he can charge into the gap and into the backfield for backside pursuit or if he should flow to the play side; it all depends on the play fit. Which leads us to the 49ers game against Seattle.

American Football Monthly has a great article on ILB Run Fits.

Linebacker Run Fits

Now I'm going to admit right away that I have not watched any film (I don't have the all 22 coaches film this year). I'm basing my analysis of the Niner's run defense off of the comments of the players and coaches. Here are a few that stuck out to me:

Michael Wilhoite

I just think that we weren't in good positions to make plays. I think that people aren't in the position they're supposed be or they're not in the right gaps, people are scrambling to make plays. When you are scrambling to make plays you aren't going to bring down a good running back with one hand or a body tackle.

Yeah, I think we prepared for whatever running back is in the game. I don't think they changed anything because it was him instead of Marshawn. I think they run the same plays that they do with Marshawn. He may run a little different but at the end of the day, football is football. You have to execute your assignment you gotta make tackles.

Navarro Bowman

That’s what offenses try to do, get the ball on the edge and get those small guys in a position where they have to tackle. That’s what they did. There are some things that when it comes to ownership and doing your job and being accountable for everything. The ball is not supposed to get out there. We’re not supposed to get out there. We’re not supposed to put our small guys in that position. They took advantage of it.

We prepared for 24, and 24 didn't play. So I don't know what kind effect that had on us, but they did a great job taking advantage of it.

Jim Tomsula

That's what I saw, along with some fit problems where we weren't tuned up in the fit there. And again, there was that counter play happening that hit us a couple times and it's not really new, it was just a little bit different and just fitting that up and being detailed in those fits was where I saw those, our biggest problem."

So basically I think it was the fact that the Niners prepared to face Lynch and not Rawls. Lynch is primarily an inside running tackle breaking machine. Rawls is a faster tough runner that breaks DB tackles. If I were going to game plan against Lynch I would want to push him outside. It's not that he can't run outside but it's not his strength. Rawls on the other hand is fast enough to turn the corner so is all to happy to get pushed outside. Lynch could take on a force player on the outside and bowl him over but not before backside pursuit or the alley player gets their to help tackle him. Rawls is fast enough to stretch out the play, run over the force player defensive back and keep going. If the goal was to spill the ball carrier then all the defensive linemen were trying for inside fits and may have been out of position on many plays.

As far as inside linebacker run fits against the zone stretch, If I'm preparing for Lynch I want the backers to look to fit the A and play side B gaps or at least keep an eye on them before flowing to the ball because Lynch usually looks to turn it up field immediately when he sees a hole in the interior of the defense. But if the inside backers are preoccupied with the inside gaps then Rawls has a much easier time running to the outside against the DB force players.

I think defenses being unprepared for certain kinds of players and run schemes also explains some of the success the Niners had against the Vikings in weak one. The Niners were under Harbaugh/Roman primarily a gap blocking and inside zone run team. The 49ers ran outside zone stretch plays over and over again. The keys and fits for those kinds of plays are much different and I believe it put the Vikings at a huge disadvantage.

This is a FanPost and does not necessarily reflect the views of Niners Nation's writers or editors. It does reflect the views of this particular fan though, which is as important as the views of Niners Nation's writers or editors.