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Film Room: Feeling Constrained

Coach Bussen takes a look at the role run constraints played in the Kentucky game.

NCAA Football: SE Missouri State at Missouri Jay Biggerstaff-USA TODAY Sports

For the most part, offensive coordinators must call a play based on what they believe the defense will do on that snap. But defensive coordinators can be tricky and unpredictable. A run play can be stopped cold by an unforseen safety dropping into the box. A pass can be snuffed out by an out-of-the-blue max coverage.

But offensive coordinators can be pretty crafty themselves, and implement mechanisms within their base plays so that — in theory — their calls are the right ones every time. These are called constraints. A constraint anticipates a defensive strategy that would compromise the base play, then gets the ball to a space that is weakened.

In this installment of Film Room, we will look at a few constraint plays Missouri used against Kentucky.

But first, a quick primer on the constraint system.


An RPO, or Run/Pass Option, is a popular version of a constraint design. The point of an RPO is to put a single defender in a conflict situation.

As an example, here is a very common RPO that pairs a Zone running play with a backside slant route.

The Will linebacker, in red, is the conflicted player. The backside offensive tackle, usually stepping playside on Zone, is checking back for the backside defensive end, meaning the Will will be unblocked. If the Will steps forward to play the run, the quarterback pulls the ball from the running back’s belly and throws the slant in the open window.

If the Will drops or stays in the slant window, the quarterback simply hands off to the running back.

Here is an example of Missouri running this play earlier in the season against West Virginia.

The Will, WVU’s #17, aligns just outside the run box and shuffles forward on the snap. Kelly Bryant pulls the ball from Tyler Badie (#1), and pitches to Albert Okuwegbunam (#81) on the Slant.

As RPOs have gained in popularity with offensive coaches, RPO has also become a term commentators like to throw around. And not always with precision.

To my mind, we should distinguish between RPOs that involve a post-snap read such as the example above, and constraint options such as quick passes and screens attached to run plays that call for a presnap read. I tend to think of the former as true RPOs, as the term only came into use with the advent of this post-snap-read tactic.

Quick Pass Constraints

The idea behind a quick pass constraint is to protect the run play from extra defenders putting themselves in position to make a tackle.

Here is a diagram of the constraint scheme with which we’re probably most familiar: a Bubble Screen attached to a run play, in this case Inside Zone.

First let’s notice that there are two read players, the strong safety (S, in red), and the backside defensive end (E, also in red). This is the major difference between post-snap RPOs and presnap constraints. If the quarterback chooses, presnap, to go with the Inside Zone, he can’t read the end and monitor the movement of the strong safety during the play. The play becomes a run/run option: the quarterback will handoff or keep. In a true RPO there is only one player to read, allowing the QB to make a handoff/pass read post-snap.

So how does the quarterback make his presnap read in this example? He is checking the strong safety’s alignment and presnap movement. If the strong safety is not in position to play the Bubble at the snap, the quarterback will flip it out to the receiver.

In this example, the strong safety’s alignment takes him out of the picture for the Bubble, so the quarterback throws it that way. The outside receiver blocks the most dangerous man between the cornerback and the free safety. If the cornerback has force reponsibility (this is called Cloud), he will be the one to attack the screen. If the safety has force (Sky), he will show as the most dangerous man.

The quick screen is beneficial because it gets the ball to a receiver in space with numbers in the offense’s favor. But its most important function is protecting the run play.

With the strong safety defending the run, the numbers advantage is in the defense’s favor. Let’s return to our example to see the effect the safety’s aggression has on the Inside Zone.

The strong safety blitzes off the backside edge and the line slants away from him. At first blush, this does not seem like a problem, as the strong safety becomes the end man on the line of scrimmage (EMOL). The quarterback can read him to decide on a give to the running back or a keep. But notice that the extra defender means the offense cannot block the Mike linebacker (M, in orange).

This is not ideal, but the Bubble screen allows the offense to avoid running the ball into an unfavorable box, and offers a chance to make yards in an area where the defense has weakened itself.

If the defense brings the strong safety off the edge but doesn’t slant the line, the Mike can be blocked. But now there are two defenders on the backside edge of the Inside Zone. The end can take the running back, and the safety can take the quarterback. The quarterback read has been rendered useless.

As in the previous scenario, the ball should go to the Bubble on the outside.

Other quick passes as constraints

Now Screen

The Bubble seems to have gone out of fashion. These days a more common quick screen is what’s sometimes called the Now Screen, as seen here in a play against Wyoming.

The Tigers align in an unbalanced set here, and Jalen Knox (#9) makes himself immediately available for a quick screen. Bryant doesn’t throw it because the threat of the screen succeeds in keeping the strong safety (Wyoming’s #8) sufficiently out of the box.

Shoot Screen

Another quick screen that has gained popularity is the Shoot Screen. The inside receiver runs a Shoot route and the outside receivers block for him. This touchdown against South Carolina is an example of a Shoot Screen featuring Albert O.

I suppose the skip across the goalline is a tribute to Albert’s former teammate Damarea Crockett, a frequent practitioner of the TD-hop.

A couple observations.

  • This is not a run constraint, it’s a called screen. But it very well could be used as a run constraint with a play such as Inside Zone, which would look like this.
  • On the broadcast, the announcers suggested that the Tigers got away with downfield blocking on a pass. This was incorrect because Albert caught the ball behind the line of scrimmage. That makes the play a screen, so blocking downfield is legal.

Hitch Constraint

The final quick pass constraint I’ll mention is the Hitch route. This is a scheme Drew Lock often used to his advantage last year.

Here is an example from the Lock era that combines an Outside Zone with a Hitch constraint and a Now screen.

The play diagrammed.

Georgia does not put an extra man in the box, but they attempt to set a trap for Lock. The strong safety turns his body to the #2 (middle) receiver making the Hitch to #3 (the inside-most receiver) appear to be wide open. This alignment removes the possibility of the Now in Lock’s presnap read. But the safety aggressively falls in on the Hitch at the snap. Nevertheless, Lock is successful in squeezing the ball in to his tight end, Kendall Blanton (#11).

And that’s my too-long preferatory discussion of constraints. Let’s get to some plays from the Kentucky game where the Tigers made good use, and not so good use, of run play constraints.

Constraints vs. Kentucky

I’ve isolated a two-play series where Missouri used constraints well to apply pressure to the Wildcat defense, and another two-play series where they missed opportunities to do so.

We’ll look at the negative plays first.

Constraints Constrained

Play One

On this play, Mizzou runs Inside Zone Search to the left with Hitch constraints to the right.

Notice that Kentucky’s strong safety aligns at the apex, halfway between the slot receiver and the backside tackle, then blitzes off the backside edge at the snap.

The blitz puts slot receiver Johnathon Johnson (#12) one-on-one with the free safety. The safety squats on the Hitch, and Bryant is forced to hold the ball. This is a busted play, but Bryant succeeds in making something out of nothing, scurrying for four or five yards.

I’d like to have seen Johnson work a bit harder at getting to the safety’s inside shoulder, making himself available to Bryant. But you’d also have to tip your cap to Kentucky for anticipating the scheme Dooley would use, and using a blitz to trigger a well-defended constraint throw.

Play Two

One the very next play, the Tigers run a Tackle Lead, again to the left. This time there does not appear to be a constraint on the backside.

Once again, the strong safety blitzes off the edge, and this time he is followed by the free safety.

Here is the play diagrammed.

Note that the Wildcats have two players on the backside edge of the run play. As we saw above, this makes a quarterback read ineffective: one player will take the running back, one will take the quarterback.

The boundary safety is bluffing a single-high coverage and is late getting over the slot receiver Jonathan Nance (#4). This would be the perfect situation to throw the Hitch constraint.

But, alas, no constraint was called. The strong safety tracks down Larry Rountree III (#34), who manages only a one-yard gain.

Effective Constraints

Play One

Here the Tigers are running Outside Zone to Dawson Downing (#28), with a Now Screen on the backside.

The presnap read is the strong safety (S, in red).

Bryant judges the safety to be tight enough to affect the run play. (He also probably peeks at him after the snap when the safety shuffles inside. Earlier I called for a hard distinction between presnap and post-snap reads. Now I’ll admit there is often some gray area.)

Bryant whips the ball out to Nance (#4), who picks up a first down.

This was fine execution by the two senior transfers.

Play Two

On the very next snap Missouri runs the very same play, Outside Zone with a Now Screen constraint, and out of the same formation. This play is especially illustrative as it shows the full power of the constraint tactic as it unfolds into a triple option scheme.

The Wildcat defense gives a different look on this snap, playing a linebacker on each edge and the strong safety inside—a seven-man run box.

The boundary safety, aligned over the backside slot receiver, blitzes from depth on the snap.

Because the blitz comes post-snap, Bryant’s presnap read is to go ahead with the Outside Zone. The outside linebacker — the backside EMOL and therefore Bryant’s run read — crashes down on the running back, Downing (#28), triggering Bryant to keep the ball.

Bryant now heads to the alley — the space just outside the backside tackle — and enters the second phase of the play, reading the alley. Again, this is triple option football.

The boundary safety blitz takes him through the alley at the snap, preventing Bryant from turning upfield.

Bryant responds by flipping the ball out to Nance, who is maintaining his availability.

Johnson, the slot receiver, finds the most dangerous defender, the strong safety buzzing to the outside, and makes a nice block, opening a lane for Nance.

But in keeping with a theme of the game, Nance — up to this point the only Tiger receiver who had showed sure hands in the rain — drops the ball.

Let’s ignore the drop and put the phases of the play all together. Bryant makes three reads.

  • Presnap decision to run the Outside Zone or throw the Now (he elects for the run play)
  • Post-snap read of the EMOL to handoff or keep (he keeps the ball)
  • Second post-snap read to run the alley or throw the Now (he throws the screen)


Constraint plays are an integral part of modern offenses. As we have seen, proper decision-making and execution of this facet of the game is essential if an offense is going to keep numbers in their favor.

Against Kentucky, the Tigers made good use of constraints on occasion, but more often than not failed to take advantage of the power of constraint schemes.