The goal of every defense is to get off of the field by limiting the number of plays it has to absorb throughout a game.
The goal of our analysis is to track defensive efficiency by assessing the total attempts needed to gain a first down against the defense.
Why are we using this metric to identify defensive efficiency?
The why is to measure and identify what teams sustain, or fail to sustain drives by focusing on how many attempts it takes to gain a first down against a defense. The teams measured are power five only and must have faced a minimum of 3 power-five opponents to qualify.
For Example; Michigan is number one defensively at allowing first downs. According to our analysis, it took power five opponents an avg. of 4.89 offensive attempts to achieve a first down against Michigan's defense in 2017.
The top five defenses in total first down rate include four teams that are consistent top ten defenses in college football (Alabama, Ohio State, Michigan, Clemson) and Wisconsin who has built more with less on their journey to becoming a top ten defense. The Big Ten has three teams in the top five of our analysis, which speaks volumes about the growing defensive strength of the Big Ten Conference.
Two teams in our analysis were in the college football playoff (Alabama, Clemson). The lowest ranked team in the 2017 based on national polls is Michigan (mostly due to their inconsistencies on the offensive side of the ball and not their defense).
List of top, middle, and bottom five defenses:
How does this analysis correlate to total wins and losses?
We took our entire power five list and then extracted the top five, middle five and bottom five ranked teams in the analysis.
Why did we do this? We did this so that we could get a more intimate look at the diference between a top five, middle five and bottom five team.
Win, loss records combined for each group (top five, middle five, bottom five).
The top Five teams in our analysis combined win loss totals 58-11 (84% win total). Avg. Win-Loss: 11.6 - 2.2
The middle Five teams on the list include four SEC defenses, and one from the Big 12. The middle five teams combined, produced four winning records and combined total of 37-26 (58% win total). Avg. Win-Loss: 7.4 -5.2
The Bottom five teams include three SEC teams and two Pac 12 teams who produced one bowl team (Kentucky) and combined for a total win-loss record of 21-40 (34% win total). Avg. Win-Loss: 4.2 - 8
How could this translate to the 2018 season?
We can begin to hypothesize that teams with a higher number of returning starters in 2018 who were ranked at, or near the top of our list in 2017 should remain at or near the top of the list in 2018.
Percentage of returning starters for top five, middle five, and bottom five teams:
The top teams in this analysis from 2017 that return the most starters on defense are Clemson and Michigan who both return a wealth of depth and talent on their defensive fronts. You can safely assume that both Michigan and Clemson will remain in the top five of this analysis in 2018.
Ohio State and Alabama are always in reload mode every year because of the number of underclassmen they lose to the NFL draft. So we cannot assume anything with Ohio State and Alabama.
Wisconsin is the one team based on returning starters that may not return to the top five of this list in 2018. Wisconsin has begun to recruit better athletes, but they lost a lot of production from their 2017 defense. They still have a more accessible path to the Big Ten Title game (for now) coming out of the Big Ten West.
Out of all of the middle five teams in our analysis, I expect a huge jump in this category by the Florida Gators. They return 81% of their defensive starters from 2017. Florida does not lack talent, and another major bonus is Defensive Coordinator Todd Grantham who followed Dan Mullen to Gainesville.
Grantham, in only one season at Mississippi State, led a remarkable defensive turnaround coaching the Bulldogs from the 110th ranked total defense in 2016, to the 10th ranked total defense in 2017.
The next big data point is 3rd down defense. How does this correlate?
The goal of every defense is to get the offense into a predictable third down situation. We place a lot of emphasis on 1st and 2nd down in our (BGA) every play analysis.
The BGA analysis scores every play on a + or - system. Defenses can successfully limit play call options if they can force a 3rd and five plus yds to go situation. The goal of every defense is to allow less than three yds on 1st and 2nd down plays.
For example; if you gain 3 or more yds on 1st, or 2nd down we give the offense a score of +1. If the defense holds the offense to a gain of fewer than three yds on 1st or 2nd down, the offense gets a -1 score.
Third down efficiency defense for top five, middle five, and bottom five teams:
The top 3rd down defenses among the power five schools include four of the top five defenses identified on our 1st down efficiency analysis above. The one outlier is Alabama who ranked number seven in total 3rd down efficiency in 2017.
Who to look out for in 2018.
The one team to look out for in 2018 is Florida who was number five in 3rd down defensive efficiency among power five teams in 2017.
Florida went 4-7 last season and should be able to improve mightily in 2018. They return 17 total starters and 80% of their 2017 defense. The Gators were young and talented in 2017.
The key factors that can lead to a Florida resurgence in 2018 will depend on how they can improve their run defense. They return three defensive line starters and every linebacker from 2017, but the front seven struggled against power-five opponents giving up 1 point every 17 rush attempts and ranking 61st out of all FBS teams against the run, allowing 4.42 yds per rush att.