Box and Fill, or Spill and Kill?

Off-tackle runs occupy a weird space in X’s and O’s. They don’t really hit inside or outside of the box, but generally right on the edge of it. The back runs downhill, so they develop faster than sweeps, but because today’s off-tackle calls usually have pullers, outside zone blocking, and/or delayed handoffs, they aren’t as fast as downhill runs. That in-betweeness means there’s a variety of ways for defensive ends and outside linebackers to attack off-tackle plays, and particularly off-tackle plays with pullers.

Boxing and Filling

At least into the 1940’s, coaches were telling their defenders the best way of defending a gap was shoving the blocker into it. Things have changed some since then. A concept that’s more familiar to football fans today is that these older defenses understood the idea of keeping runs from getting free to the sideline. Outside of that idea, it was a little pell-mell, and sometimes the results weren’t great:

This play broke wide because the defense failed get a defender out wide enough to turn the runner back. Letting the runner get outside wasn’t too different from leaving a receiver uncovered. Watching all those cut blocks, you can probably tell that it was pretty hard for the defensive end to make a tackle, because he had to meet the block and then out-quick the runner to whatever side he ran to. So defenses came up with a compromise. The widest man on outside runs was given one responsibility: turn the run back inside. They weren’t told to mash blockers into runners, or wrestler blockers around to make clean tackles. They just had to turn the run back inside. Eventually, the guy responsible for encouraging the run back inside became known as the “force” player.

Eventually stuffing those tricky off-tackle runs mentioned at the start of the article became important enough that a specific term was applied. Depending on the team, this was called “boxing,” “containing,” “forcing,” “hard-jointing,” and maybe a few other things. We’ll go with “boxing” since it’s pretty common.

Gap-control ideas and run fits as we know them today started evolving in the 50’s, and run defense evolved from wrestling blockers into controlling gaps. In his 6-2 scheme, Bear Bryant instructed his defensive ends that about 75% of their focus was on their outside gap, and the remainder on the inside gap. A defensive end meeting a kick-out block had to keep his “outside leg free” to make sure he could box-in the runner and keep the back from going wide. The defensive end wasn’t told he had to tackle the runner, or even try to: That DE’s first job was to keep the runner from breaking wide. The reason for this was that kick-out blocks were tough to disengage from and still make a tackle. Defensive coaches figured the better plan was to route the back to where “fill” defenders coming in from behind would clean up on the tackle. 

That idea of keeping the outside half of your body free is the heart of boxing the run. Here it is in action back in ‘58:

See how his right arm (outside arm) isn’t part of attacking the fullback? If the tailback had gotten the ball and pushed to the sideline, the end would’ve been able to throw an arm around him for the drag-down tackle, or threaten him into turning so flat that the rest of the fillers would’ve been able to catch up.

Boxing was the rule for just about every edge defender until the late 1980’s. Look at this 5-3 defense and you’ll see why:

The DE has nine players inside of him, and maybe one player outside in the cornerback. If the corner is playing a zone in that area and he doesn’t mind tackling, he could be there to help on an outside run if the defensive end breaks inside of a pull. But those two things aren’t guaranteed. It’s a safer bet to get the runner going into the teeth of the defense. Even in the Bear fronts of today, the defensive end is usually the guy responsible for turning runners back.

Over time, the box-technique became pretty universal. In a base defense, a boxing defensive end would attack the outside half of a blocker with his hand or shoulder. By doing this, he got upfield and kept his outside arm free. The DE also had to keep that inside gap from getting too big so the filling defenders weren’t making tough open-field tackles. This line of thinking has stayed so stable that the same cues can be seen in this clip from 2024:

There’s a little less chicken-winging/forearm-flippering these days, but otherwise, it’s pretty much the same idea.

Power and Counter

Those cut blocks on the edges went away, but hanging around were kick-out blocks. Guards, tackles, tight ends, wingbacks, full backs, running backs, and even centers would come crashing down the back of the line of scrimmage or screaming out of the backfield like freight trains and wipe out defenders. And two of the best plays to take advantage of it were off-tackle plays: Power and Counter.

These days, Power means one backside guard pulls down the line and wallops a linebacker or defensive end who’s been left unblocked. Counter means two backside pullers are coming, as seen here:

I’d say Power’s first boom was in the 50’s, but it had a resurgence in the 70’s and 80’s with its cousin Counter. Disco/techno-era Power and Counter meant two or even three blockers were coming downhill, and typically the only difference between the two was the order in which blockers arrived at the scene of the collision. It was up to the defense to deal with all that beef and all the extra gaps created by the pullers. And that was a hassle because the defense not only had to get bodies over there to match all those pullers, it had to arrive in good order, decipher the blocks, and play them strong.

The surge in Power and Counter calls roughly coincided with both rule changes that allowed offenses to use their hands more, and the mainstreaming of steroids in the NFL. General Managers and coaches looked for huge, long-armed dudes to grab/mash defenses around, and they found them. I’m sure plenty of you recall what was probably peak Power/Counter:

Joe Gibbs’ and Joe Bugel’s Hogs weren’t the biggest lines of their era, but they were far bigger than blockers in earlier eras, and they had pulling down to an art. “Counter Trey” is the call people remember, but there was a host of kick-out plays they whacked people with.

Defenses always react, and most of them got bigger. In the 70’s and 80’s, a bulky 3-4 front was the top scheme in the NFL, and another common defense was the 5-2 with a safety running around matching up against the tight end. Getting into the late 80’s and early 90’s, though, some teams went the opposite way, though: They got smaller and faster.

Jimmy Johnson is generally considered the guru and biggest innovator of the trend. When he took over Miami with his speedy, swarming, Wishbone-stuffing 4-3 defense, offenses didn’t know what to do. The catch for smaller defenses was handling those Power and Counter pulls. The converted linebackers playing defensive end had a hard time boxing the gaps and dealing with the pounding of those huge bodies; the Florida/Georgia clip is a good example of the size discrepancies that can occur. So, Miami and other small defenses flipped the script. Instead of jamming the runner inside by boxing him in, they made him run outside.

Spill and Kill

The term was “spilling.” Instead of boxing off-tackle runners for downhill linebackers to clean up, Miami spilled them wide. Backs want to run downhill on off-tackle plays, and spilling could wreck that. It made the backs run laterally to zone DBs or simply slowed them up enough for a wolfpack of scraping linebackers to run them down. To help the cool factor, coaches called it “spill and kill,” instead of “spill and fill,” though maybe the best phrase for it was “scream and splatter.”

The technique of spilling was the reverse of boxing. When the defensive end felt the downblock away from him, he got flat and ran down the line of scrimmage. Instead of keeping his outside arm free, he charged it into the blocker and tried to cause a pile-up. To help players who had been boxing from Pop Warner through high school adopt the practice, coaches called the technique “wrong-arming.” Because these collisions happened well inside the box, the DE got there before the pullers gained too much speed, and they caused problems for the RB’s running track early in the play.

While the play behind the spill is rough, you can see how the end-man disrupts the blocking so badly he nearly makes the tackle.

Tom Osborne’s run with the Cornhuskers is the other contender for best Power/Counter team in football history. In fact, Joe Gibbs grabbed a ton of gap-scheme goodness from the Huskers. The Huskers’ games against Johnson-led Miami were a demonstration of how the game was changing, as the Osborne was wary of running much Power or Counter against the Hurricanes.

Bud Foster was another defensive mind who incorporated some spilling to help his speedy defense. The original UW 4-4 that Phil Elmassian brought to Tech didn’t spill. It had eight or nine guys in the box and firing into the backfield from every direction on nearly every run play, so it wanted runs funneled into all those defenders. But as offenses started spreading the field a little more, Foster started spilling off-tackle runs. Those spills often went to the Whip player hanging out in the alley. The Whip was often unblocked and able to blow up plays.

One problem with both techniques is that boxing and wrong-arming generally take the defender out of the play. Rushers can wrap around a pulling blocker and make a play from behind, but it requires a bit of luck for even very talented defenders. TyJuan Garbutt pulled it off a few years ago:

The other 99.9% of the time, though, it’s a one-for-one trade: One rusher and one blocker canceling each other out. Watch enough of those old Redskins clips and you’ll see that Lawrence Taylor himself had a hard time beating the kick and then making the tackle. I’m going to credit former Boston College and Michigan defensive coordinator Don Brown for coming up with a trick that helps this issue. He called it the “dent” technique: It’s still a spill that pushes the runner wide, but the execution is different. The defensive end attacks the inside shoulder of the blocker, same as the spill, but he shuffles square down the line and uses his hands to attack the block. This lets him keep his feet and his vision on the runner, giving him a better chance of helping with the tackle, while presenting a small target for the blocker. The dent technique is easier with slightly bigger players, but they don’t have to be hulking beasts to make it work. This is because it’s so hard for pullers to turn on a dime and rock defenders who are squeezing down and staying close to the LOS.

Brown’s teams were so good at denting that I had a hard time finding examples because offenses didn’t run much gap-scheme stuff against them. I also I don’t recall seeing any other teams using the technique, but it’s still worth mentioning. I’ve also seen DE’s take pullers head up and then slide inside, and some folks call this a “dent,” but it’s not the same as what Brown taught.

The Big Picture

So, from the 90’s all the way up to today, defenses have mainly had two different ways to deal with off-tackle pullers. Offenses have the option game, and have added plays like Split Zone that work similarly, but boxing and spilling are still the top dogs for defenses. It’s rare you see defenders smacking into pullers head-on; when you do see it, it’s usually because the defender screwed up.

There are reasons to embrace both concepts. Boxing is easy to teach, feels more natural, and generally directs the runner to the team’s best tacklers, i.e., the inside linebackers. But it prefers bigger defenders and doesn’t disrupt the offense’s intent.

Spilling attacks blocks faster and more thoroughly, forces backs into lateral runs, and lets smaller defenders have an outsized impact. But it’s intensive to learn, sends the ball away from the heart of the defense, and restricts coverages more.

Spilling tends to work best in four-down defenses. In college, most 4-2 and 4-3 schemes pick either boxing or spilling to major in, but use both. For a lot of defenses, the choice of technique is situational. The defensive coordinator wants to align a specific way or cover a certain way, and based on that, either spilling or boxing makes more sense.

In college and the NFL these days, I’ve seen more boxing than wrong-arming. Some of that is blockers have gotten better at adjusting to spill players, and bigger defenses that favor boxing are more popular than they were in the 90’s and early 2000’s. I think the biggest impetus, though, might be the rise of the gun-option running game with heavy formations. Defenses want to keep eyes on the QB/RB meshpoint, which you can’t do while screaming down the LOS like a bullet, and the multiple-TE formations don’t spread the field like three- and four-receiver sets do, which can remove fill players from spill calls. This being football though, the teams that still wrong-arm some get a boost from going against teams that aren’t used to seeing it. The Philadelphia Eagles of the past few years are a good example.

What About the Hokies?

The Hokies have moved away from spilling since Foster retired; based on his history and influences, I don’t think that’ll change with Siefkes, but anything’s possible. And who knows, it might be a wrinkle that catches some teams unprepared.