The Impact of Defensive Yards Per Game & Yards Per Play on Def Points Per Game
Sometimes coaching clichés are true and sometimes they are not. I recently published an analysis around the predictive strength of Defensive Points Per Game and its effect on wins. My analysis uncovered that Defensive points per game has a stronger effect on wins than Points per game, so the narrative that defense is any less important than scoring offense is simply not true. So, if Defensive Points Per Game is a strong predictor of wins, what are some of the areas that have an effect on Defensive PPG?
The focus of this analysis was to see what impact Defensive Total Yards Per Game have on scoring defense and if there is any truth to the old philosophy of "Bend, Don't Break". As I started digging into the data, this old coaching cliché kept creeping back into my head. The more I analyzed, the more I started to realize that this coaching cliché was simply NOT TRUE.
In fact, according to my analysis, the new mantra around defense should be. Defense: Don’t Bend & You Won’t Break.
Before we get into the effect of Def yards per game on Points, lets’ start with the obvious and visit where this old mantra originated. Giving up touchdowns is bad and the more touchdowns you give up , the more points per game you give up. In fact, the predictive strength for Touchdowns on defensive points per game is 87%. That should be of no surprise to anyone, however, did you know that according to my analysis of 2018 data, both Defensive Touchdowns and Defensive Yards Per Game are equally good at predicting Defensive Points Per Game, essentially disproving the “Bend But Don’t Break Mantra”. Fact is, if you give up yards , you will give up Points!
Defensive Yards Per Game Strongly Drives Defensive Points Per Game with a Predictive Strength of 84%
Sure “bend but don’t break” in THEORY is great. The idea is that it is ok to give up a lot of yards, just don’t give up touchdowns. This has become a rallying cry for teams & defensive coordinators who see their opponents marching up and down the field against them or from a broadcaster looking for a catchy phrase when a team happens to get a stop after a long drive. In theory that all sounds fine but in REALITY it's simply not the case (Just take a look at the bubble chart above once again). Sure there are times within a game when a team gives up a long drive or a ton of yards and comes up with a crucial stop to win a game but over the course of a season it’s a losing bet with an 84% chance of losing!
You can see from the chart above how Defensive yards per game effects defensive points per game. All 130 FBS are placed into 5 categories for Def Yards Per Game. The low group who give up less than <338 yards per game give up 18.8 points per game on average while the high group gives up more than >446 yards per game give up an average of 37.31 points per game. You can also see where the middle 3 groups lie in terms of yards and points PG respectively. This charts above is evidence why I urge all you Defensive Coordinators to adopt the new mantra of “Don’t Bend & You Won’t Break”
Defensive Yards Per Play Predicts Defensive Points Per Game 71.6% Predictive Strength
In addition to total yards per game, another important area that correlates directly to points per game is Def Yards Per Play. What you see below is a decision tree that shows the predictive relationship between yards per play given up on defense and the predicted points per game. The darker the color on the tree = the higher yard per play average and the higher the amount of points per game given up.
Below you will see the same information in a more descriptive format. Look at the images below in 3 columns. Down the left hand side you see the Predicted Value, which is the predicted total of Defensive Points Per game correlated with the middle column of Defensive yards per play average. The far right column (Records) tells you the number of teams out of 130 FBS teams that fall into that category. So for example, the very first row tells you that 28 teams or( 22% of FBS teams) gave up on average more than >6.14 defensive yards per play, so the predicted total of defensive points per game is 36.69 points per game (Not Good). Compare that to the low group who gave up less than 4.96 yards per play which leads to a predicted points per game of 18.95.
The difference between an 8 or 10 win season or a bowl game or nothing is truly just a matter of inches on each play
As you can see from the images above, the difference of a 1 yard or less per play on average can equate to 4, 5 or sometimes 6 more points per game. If you recall back to my analysis on the impact of Defensive Points Per Game on Wins, you will know that 4-5 less points per game can mean the difference between quite a few wins and losses. Just look at the teams in the middle groups and how how much different your season would be giving up 24.06 PPG vs 30.94 PPG or even 18.95 PPG vs 24.06 PPG. The difference between an 8 or 10 win season or a bowl game or nothing is truly just a matter of inches on each play.
I hope you enjoyed this breakdown of how Defensive Yards Per Game & Yards Per Play and impact Defensive Points Per Game. As always , feel free to reach out to me for additional questions and analysis info@acefootballanalytics.com and please join our site for more analysis. Coaches can always contact me for additional analysis and consulting.
Below you can see all 130 FBS teams, where they rank by Def yards Per Game. The first column shows Def Yards Per Play and the last is Defensive Points Per Game.
