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By The Numbers: 2014 Defensive Performance

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Defense By the Numbers: Part 1 of a Series

Robert Hanashiro-USA TODAY Sports

With the college football spring practices over and the lull until fall camp, we thought it would be a good idea to break down some of the more overlooked statistics and analyze the different aspects of defense. There will be several articles in this series; however, we felt it important to start with the defensive units as the number one offense in the country has not won a National Championship since Nebraska and Michigan split the NC in 1997.

For the analysis, and to get a good feel for any differences, the top 10, middle 10, and bottom 10 defenses were used. From that, the top 5 tacklers from each team were looked at for production. Additionally, the full set of individual tackling statistics were analyzed. For the analysis, drive data for the 2014 season was used. (Thanks to www.fbsdrivestats.com )

Some of the key differences between the three groups are as follows:

Category

Top 10

Middle 10

Bottom 10

Combined Win/Loss Record (Bowl Teams)

85-45 (10)

77-50 (7)

35-88 (2)

Yards/Play Allowed

4.65

5.55

6.55

Plays Per Drive Allowed

4.8

5.4

5.7

% of Drives w. Scores allowed

26.3%

35.1%

52.8%

Stop Rate (yds. allowed vs. expected yds. allowed per drive

65.8%

54.5%

41.9%

Tackles for Loss / Game Average

7

5.7

5

Some quick math using yards per play allowed and plays per drive allowed shows just 1.9 yards and .9 plays per drive separate the top 10 from the bottom 10 defenses. However, when expanded over a the course of a game that translates to 15 yards per drive, 195 yards per game, and 22.5 points per game improvement by the Top 10 group over the Bottom 10.

One thing that’s was look at was the top 5 tacklers from each team in each group. The results are pretty telling. The top 5 tacklers from each team make up over 42% of a team’s total tackles; the interesting thing is which defensive unit makes the tackles (Defensive Line, Linebackers, or Defensive Backs).

The linebackers are really set up to make the majority of the tackles, simply based on scheme. The defensive line production of each group and the reduction of the defensive backs’ % of tackles does make a huge difference in performance.

Below is the percentage of defensive tackles for each group (special teams and tackles made off of turnovers were not used).

Once again the defensive line for the Top 10 shows an increase in defensive line production and a reasonably proportionate decrease in the DB’s tackles.

While looking at the aggregate tackles for each group, a curious trend shows up. The total tackles for the Top 10 is significantly less than the other groups. This is mostly because of the effectiveness of the respective teams; but it does not explain the whole story.

Below are the aggregate tackles by group and defensive unit.

The Top 10 group made 1,227 less tackles, in 7 more games, than the Bottom 10; this translates to 2.5 possessions per game for the Bottom 10’s opponents. As said earlier, most of this is attributed to the difference in the defensive efficiencies of the groups. However, there is another part of this that will need some further analysis and that is time of possession (TOP). The median rank in TOP for each group is as follows:

Top 10: 16.5

Middle 10: 63

Bottom 10: 114

When teams are looked at for predictions, this is a good reason why the statistical analyses are based on offensive and defensive efficiencies. It is very enjoyable to watch teams like Western Kentucky, North Carolina, Texas Tech, and Baylor run a prolific offense. However, these teams (the first three in the bottom 10 in defense) do not allow their defenses to get the rest that is needed, nor do they have the depth on defense to be able to play most of the game on the defensive side.

Regardless if TOP being any major factor, that will be explored in the future. For tomorrow a deeper analysis into defensive efficiency and consistency…..which are large pieces in breaking down games and teams performance…. Will be conducted. From that we will develop a defensive power rating for each team.

Enjoy.