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How the Bills used James Cook to attack the Chiefs defense

Breaking down why the Buffalo running back was so productive in the Chiefs’ Week 14 loss.

NFL: Buffalo Bills at Kansas City Chiefs Denny Medley-USA TODAY Sports

This Sunday, the Buffalo Bills had a clear plan to attack the Kansas City Chiefs defense, which was deploying running back James Cook in various ways. On the day, Cook finished with only 10 carries for 58 yards, but his five catches for 83 yards and a touchdown hurt the Chiefs more than anything. The Bills had a concentrated effort to get Cook the ball — particularly in the first half — and were able to achieve offensive success through him.

Cook is a hyper-athletic running back who is talented as a receiver in open space, and they found many ways to take advantage of his speed and athleticism on Sunday.

How exactly were they able to get Cook going? Let's break down the film on Buffalo's gameplan:

Finding Cook out of the backfield

To start the game, the Chiefs lost Cook on the first play. The Bills go under center and run play action. The Chiefs are in Cover 4 and defend this two-man route concept well, and defensive end Mike Danna has a nice dip on the right tackle's inside shoulder to get into the backfield.

However, linebacker Willie Gay loses Cook as his eyes are locked onto quarterback Josh Allen, allowing too much space on a play that was otherwise very well defended.

The Chiefs were willing to play man coverage with their linebackers against Cook underneath, which was a mistake that they later adjusted. Before that, the Bills deliberately got Cook against any linebacker in man coverage, and Allen was willing to pepper him all night underneath.

On this play, the Chiefs are in Cover 2-man — one of their more common coverages in the first half — and were able to get Cook one-on-one with linebacker Nick Bolton on a choice route. With Cook able to win on a two-way go, Bolton isn't quite rangy enough to recover to a player of Cook's speed, which allows this second-and-long to become a third-and-short.

The Chiefs adjusted in the second half by having their linebackers "green-dog" — tracking the running back before deciding whether to blitz or cover — or just playing more straight zone coverage. Before that, they were giving too much space for a linebacker to cover Cook in man coverage.

Struggling with Cook's gravity out of the backfield

The Bills ran a variation of the same route concept twice, both times taking advantage of the Chiefs linebackers and their rules against this motion. The Bills run their H-Back, Reggie Gilliam, on a swing motion after motioning him into the backfield. This is designed to hold the defense's eyes, especially after they leak Cook behind the motion. The motion is intended to serve as a lead block for Cook while also getting four eligible wide receivers on the same side of the formation.

Both times the Bills did this, Gay was late to read the back-side leaking player since the motion into the block with the swing route alters the rules of the Chiefs' coverages. Overall, the Bills could formationally trick the Chiefs linebackers with their rules, opening concepts on the back side.

Gay has to better recognize these players, but it's also worth shouting out the design.

Cook running routes downfield

I'm not sure exactly what coverage the Chiefs are in on this play, but the broadcast caught an angle of Reid tapping his chest after this touchdown, so he took responsibility for this breakdown. My guess is that after the Bills motion into a 4x1 Nub formation, with the way safety Mike Edwards rotates into the flat, he's expecting safety Justin Reid to "rock-and-roll" over the top to play single-high safety. Reid should take anything vertically from the No.3 spot, where Cook runs the seam route.

Reid, however, doesn't roll over the top with the formation switch. By the way Reid plays this, my guess is he's "poaching" the back-side crosser from Cover 4, but he should be over the top for single-high. Regardless, the motion and numbers shift from the offense confuse the defense, and Cook gets to run in for an easy touchdown.

This is another coverage breakdown where I'm not quite sure what the Chiefs are in, but based on how this coverage looks, it looks like they're in a Quarter-Quarter-Half shell. On Gay's side, the Chiefs should be in cloud coverage, where the cornerback should squat in the flat and then carry the wheel. However, this play could also be 2-man on the back side, which would then mean Gay has to carry Cook on the wheel.

Regardless of whether this should be man or zone to Cook's side, the Chiefs weren't ready to deal with checks where Cook came out of the backfield. They buttoned up their errors in the second half, but it was a bit too late by that point. Moving forward, the Chiefs will have to do a better job against late releases by running backs and how to distribute that in their zone coverages.

Creating an advantage with Josh Allen's legs

One run concept the Chiefs had trouble defending was "Dart." Dart is a run concept where you have your back-side tackle pull all the way around to block the back-side defensive end, with all four linemen working the opposite way. The Bills took advantage of this concept in a smart way with their formations.

The Bills would frequently get into 4x1 formations, which the Chiefs responded to with two-high safeties. The choice to play two high safeties put the Chiefs in serious run-pass conflict. With three eligible wide receivers to one side, the Bills had the threat of any screen RPO attached to this play. On top of that, Allen's ability to read the front-side defensive end and run made it so the Chiefs had to respect that.

Because the Chiefs had to respect both the RPO and read-options threats, it left five defenders to deal with five offensive linemen, and Cook could use his vision to find a ton of space. The Chiefs would later adjust by inserting their safety into the run fits more aggressively, but it took a half to get there. Before that, the Bills had the Chiefs beat formationally, and the Chiefs couldn't find counters.

The bottom line

I was rather upset after the Chiefs' defensive performance, but this week was much better. I don't think the Chiefs necessarily executed their game plan poorly. They didn't let Josh Allen scramble into open space too often and were able to take away any free-access throw to Stefon Diggs with L'Jarius Sneed.

However, the Chiefs didn't have a good game plan to deal with Cook. Cook's speed downfield and horizontally put the Chiefs in a lot of conflict defensively. They were often caught scrambling and out of position, mainly due to Cook's unique skill set as a receiver.

The Chiefs made good adjustments in the second half, but it was too late by that point. The Chiefs' defense doesn't have the margin of error to overcome one lousy half with the state of the offense. Going into the playoffs, they can't afford to go one half where the offense dictates the matchups and what the Chiefs respond with. I expect them to learn from this and improve.

It's Game Time.

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