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Is the Chiefs run defense inconsistent?

NFL: Denver Broncos at Kansas City Chiefs Jay Biggerstaff-USA TODAY Sports

I was having a discussion with someone from Pats Pulpit the other day about the Chiefs run defense and I did something pretty much all sports fans do: I made a claim without any evidence to back it up.

The Chiefs run defense is boom or bust. It seems they give up big running plays frequently, but they stuff the run frequently as well.

Is that true? Let’s dive in ...

Is the Chiefs Run Defense Boom or Bust?

How can I prove this? I decided using standard deviation would be the best bet. The standard deviation is a value that describes how the numbers in a dataset differ from the average. For instance, a high standard deviation would mean the numbers are spread out. A low standard deviation would mean the numbers are mostly close to the average.

Armed with the tool of standard deviation, I decided to track each AFC teams average yards allowed per rush, and the standard deviation among the rushing yards allowed. The Chiefs run defense is one of the most consistent units in the entire AFC.

Average Yards Allowed and Standard Deviation

Team Rush Y/A STDEV
Team Rush Y/A STDEV
Patriots 3.9 5.0
Chiefs 4.5 5.2
Texans 4.2 5.4
Colts 4.7 5.6
Chargers 4.1 5.9
Broncos 4.5 6.3
Bengals 4.6 6.4
Jaguars 3.9 6.5
Ravens 3.8 6.5
Bills 4.7 6.5
Raiders 4.7 6.6
Browns 4.8 6.6
Steelers 4.2 6.6
Titans 4.3 6.8
Jets 4.2 7.0
Dolphins 5.1 7.1

The only run defense that is more consistent than the Chiefs is New England’s. Don’t get consistency confused with playing well as the Chiefs are tied for the ninth best yards per carry in the AFC.

With the Chiefs lack of variance in rushing yards allowed my boom or bust belief was kind of shot to crap. But why? Why do these teams have different standard deviations? What makes the Patriots and Chiefs run defenses so consistent?

Big Plays in Both Directions

First I need to explain a couple of terms I made up.

Stuff - A stuff is when a defense holds a rusher to two or fewer yards on a run play

Bluff - A bluff is when a defense allows a rusher to gain 10 or more yards on a run play.

I tracked each teams run plays of fewer than two yards allowed and more than 10 yards allowed. Below are the stuff percentages for each AFC team’s run defense.

AFC Run Defense Stuff Percentages

Team Stuff %
Team Stuff %
Jets 0.513
Chargers 0.495
Steelers 0.489
Ravens 0.481
Jaguars 0.474
Patriots 0.455
Texans 0.450
Titans 0.444
Bills 0.438
Bengals 0.418
Raiders 0.406
Dolphins 0.400
Browns 0.389
Chiefs 0.373
Colts 0.369
Broncos 0.368

I went and checked the correlation between Stuffs and rushing yards per attempt. There was high correlation - this means the defense who is better at getting Stuffs often will have better rushing yards allowed per attempt stats. Makes perfect sense.

The Chiefs are 10th in the AFC in run Stuffs, while the Broncos are 12th.

Now lets take a look at run defense Bluffs.

AFC Run Defense Bluffs

Team Bluff %
Team Bluff %
Broncos 0.086
Patriots 0.090
Jaguars 0.095
Chiefs 0.097
Ravens 0.097
Raiders 0.099
Titans 0.102
Texans 0.108
Steelers 0.112
Chargers 0.115
Browns 0.122
Bengals 0.125
Jets 0.132
Colts 0.133
Bills 0.144
Dolphins 0.145

Once again I checked the correlation between Bluffs and yards per rushing attempt allowed. The numbers showed that teams who yield higher percentages of Bluffs often allow higher yards per attempt.

The Chiefs are tied for fourth place in the AFC in regards to run defense Bluff percentage.

The Chiefs run defense has not been boom or bust because they don’t get a lot of Stuffs and they don’t allow a lot of Bluffs.

The Chiefs run defense has been the epitome of the old cliche: bend but don’t break. I believe Eric Berry has been a key component to this stat through 2016. How many huge runs have we seen him save this season?

We know the Chiefs run defense has not been boom or bust, but that doesn’t quite completely answer the whole consistency question.

Consistency Through the Season

The next step is to see if the Chiefs defense has been consistent on a week to week basis. We’ll do this by comparing the Chiefs run defense’s yards per attempt allowed, and the average yards per attempt of their opponent.

For instance, in Week 16 against the Broncos, the Broncos average 3.6 yards per rushing attempt on the season. In the game the Chiefs allowed 4.5 yards per attempt. The Chiefs allowed 1.25 times more yards per attempt than an average opponent had.

The Chiefs run defense began playing well in Week 10 and enjoyed a nice five game stretch where they consistently held their opponent to fewer yards than they average.

The beginning of the season was rocky, but as the year has progressed the Chiefs run defense has become more stable.

Why the rocky bumps though? Each week has a reason.

  • Jaguars - Blake Bortles ran for 54 yards on six attempts
  • Chargers - Melvin Gordon shocked a lot of people by being much better than he was
  • Steelers - What didn’t they do right in this game?
  • Jets - Powell had four attempts and 30 yards
  • Colts - Andrew Luck had nine attempts for 60 yards

So what’s the reason behind the better, more consistent play that began during Week 10?

Injuries and Bob Sutton

I don’t have a direct answer for the question above, but I do have two theories.

The first theory is injuries.

The Chiefs lost Allen Bailey in Week 6 and Jaye Howard in Week 9. Both players are solid defensive lineman who are known to play the run well. However, the Chiefs were blessed to have a player like Chris Jones waiting in the wings. It could very well be possible the Chiefs run defense is playing well because of injuries.

Not only did Chris Jones step up, but players like Nunez-Roches, Jarvis Jenkins, Kendall Reyes, etc. have all stepped up and contributed valuable playing time. These players may not have gotten their opportunity to shine had there been no injuries along the defensive line.

The second theory is Bob Sutton.

I’ve written a couple of articles about injuries to key players and the impact it has had on the Chiefs defense in the past. The impact seems to be minimal.

The Chiefs defense hasn’t struggled until three key players have gone down with injury. I would consider Derrick Johnson, Eric Berry, Justin Houston, Ron Parker, Dontari Poe, and Marcus Peters to be the key players on the Chiefs defense.

Bob Sutton has done a fantastic job scheming the defense and is capable of fielding good defenses while missing key players.

So Is the Chiefs Run Defense Consistent?

Yes and no.

Through the start of the season it was very rocky, but as the season progressed the Chiefs run defense has become more consistent and more efficient at stopping the run. So on a week to week basis the Chiefs run defense has become more consistent (and better) over time.

On the other hand, the Chiefs run defense has been very consistent on a play by play basis. This is incredible due to the number of injuries the Chiefs have sustained along their defensive line.

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