What Team Returns the Most on Defense?

This is part 2 of my diaries on returning defense. This is shorter than my other diaries, only dealing with the total returning defense and the total number of returning contributors. In my opinion, the information contained within is much more interesting than the information contained within Part 1.

However, for reference, here’s the first part of the diary on defense: Part 1.

As a side note, I make extensive use of Z-scores in this diary, which are simply standardized scores, representative of how many standard deviations above or below the mean the raw scores are. These scores are helpful in this scenario because they allow us to quantify the difference between teams in each category of returning offense.

Here’s a good resource for more on Z-scores: http://statistics-help-for-students.com/What_are_Z_scores.htm

Now for the fun stuff:

I. Total Returning Defense

To calculate the total returning defense I gave a 40% weight to returning tackles and a 15% weight to each of returning tackles for loss, sacks, interceptions, and forced fumbles. I believe that the number of returning tackles are more indicative of returning experience than any of the other measurements, hence the added weight given to them in my formula. 

Top 3 Returning Defenses

1. MSU

2. Ohio St.

3. Michigan

Worst 3 Returning Defenses

1. Air Force

2. Alabama

3. Notre Dame

Teams on the schedule return an average of 57.84% of their defense from last year, σ=15.02. The minimum value for returning defense is 37.03%, while the maximum value for returning defense returns 79.31%.

MSU (79.31%, z=1.43) returns the most on defense, followed closely by Ohio St. (78.77%, z=1.39). Michigan follows behind MSU and Ohio St. (73.15%, z=1.02).

Air Force returns just 37.03%, z=-1.39, of their defense from last year. Alabama follows behind Air Force, returning 42.40%, z=-1.03, of their defense from last year. Notre Dame narrowly beats out Alabama returning 42.72%, z=-1.01.

II. Returning Contributors

When looking at these numbers, keep in mind that I did not adjust for total number of contributors on defense last year, special team tackles, or offensive tackles on turnovers. You’ll notice that the number of returning contributors is only loosely correlated with returning defense.

Top 3 Teams with the Most Returning Contributors

1a. MSU

1b. Nebraska

2. Illinois

The 3 Teams with the Fewest Returning Contributors

1. Air Force

2a. Minnesota

2b. Northwestern

Teams on the schedule return an average of 29 contributors on defense, σ=4.12. The minimum number of returning contributors is 25 while the maximum number of returning contributors is 37.

MSU and Nebraska both return 37 contributors on defense, z=1.78. Illinois returns 32 contributors, z=0.57.

Air Force returns the fewest number of contributors on defense, returning 25 contributors, z=-1.13. Minnesota and Northwestern both return 26 contributors, z=-0.89.

Michigan returns 27 contributors on defense, z=-0.65.

As always, any comments, questions or constructive criticisms are appreciated.