Loyal Cougars

How much difference can a Bronco-led Defense make?

This morning, I set out to discover just how big of a statistical difference exists between the BYU defenses coached directly by Bronco Mendenhall and those coached by his subordinate defensive coordinators, Jaime Hill and Nick Howell. The difference was quite larger than I expected.

First, allow me to explain the comparisons I made and the data I used. For the purposes of this discussion, I began by separating the games from 2005-2014 based on who was calling the defensive plays. I realize that Bronco called the defensive plays for a few games at the end of the 2014 season, but it was not a full defensive takeover as was the case in 2010. Hence, I counted the first 5 games of 2010 as Jaime Hill games and the entire 2014 season as Nick Howell games. The remaining games I credited to Coach Mendenhall.

Next, I found the year-end rankings for each of the offenses BYU faced (based on Football Outsiders’ S&P ratings for each season).

The final step was to choose a defensive statistical category that would best relate to each opponent’s offensive ranking and provide the best snapshot of BYU’s defensive performance in each game. Pass Efficiency Defense was a good place to start, but it ignores any rushing contribution and therefore created heavy outliers from option run teams like Georgia Tech and Air Force. Any rushing statistic created a similar problem for the opposite reason. Yards per play and 3rd Down Conversions Allowed were other categories I considered, but in the end, I decided that in the bend-don’t-break BYU defense, the #1 priority is not yards, but points. And so, I settled on Points Allowed (removing special teams and defensive scores).

I feel I need to list some of the limitations of this comparison so that the numbers don’t speak louder than they should. First, all FCS opponents were removed since their offenses were not ranked by the S&P+ formula. These data also ignore the difference in home-field advantage, which normally accounts for a swing of approximately three points. There is also no accounting for whether a game was won or lost. At the end of an overtime game, you don’t care as much that your defense gave up 50 points as long as you escaped with a win. And lastly, there is also no accounting for the relative strength of each season’s BYU defense (year-end defensive ranking, injuries, talent-level, etc.). The numbers treat every BYU defense as being equal even though the 2005 defense was ranked 81st and the 2012 defense was ranked 6th. Since the 2014 defense was ranked 49th, somewhere in the middle, it’s not too much of a stretch to leave out this variable. In the end, it’s just a straight-up comparison: how many points did the BYU defense give up relative to the opponent’s offensive strength?

I plotted Points Allowed (y-axis) against each opponent’s year-end FBS offensive rating (x-axis) and this is what I got:



Looking at the graph, the first thing I noticed is that Jaime Hill’s numbers don’t look so bad in today’s light. Yes, surrendering 31 points to the 87th-ranked Utah State offense was bad, and it’s not surprising that it led to Hill’s firing. But, the remaining four Hill games fit pretty closely with similar performances by Mendenhall-led defenses. Heck, all five are better than Bronco’s worst game, giving up 40 points to the 101st-ranked Ute offense in the infamous 54-10 loss in 2011 (admittedly, the number of points allowed by the defense here is likely skewed by unfavorable starting field position generated from 7 BYU turnovers).

Plotting trend lines for both Coach Mendenhall and Coach Howell allows us to see what an average defensive performance under each coach looks like. Only two of Howell’s twelve 2014 games fell below Mendenhall’s 8.5-year average: limiting the 80th-ranked Texas offense and the 61st-ranked Middle Tennessee offense to 7 points each. Also, allowing 55 points to the 78th-ranked Memphis Tiger offense appears, at least on this graph, to be the worst performance by a BYU defense since Mendenhall became the head coach.

With an entire offseason to dwell on that performance, it shouldn’t be too difficult to see why Coach Mendenhall has decided to re-insert himself into the defensive room and retake playcalling duties in 2015. If these numbers are to be believed, looking at the trend lines, a Mendenhall-led defense would hold the nation’s #1 offense to approximately 18 points fewer than a Howell-led defense. Even against the worst FBS offense, a defense coached by Mendenhall would limit that team to 8 fewer points than if the defense were coached by Howell.

So, what does all this mean for 2015? It means that if Bronco’s presence with the defense makes as much difference as it has in the past, you can theoretically take at least two touchdowns off the opponent’s total right now for those ranked in the top 60 (UCLA, Boise State, Nebraska, Cincinnati, Missouri, and ECU based on 2014’s offensive rankings) and at least a TD and a FG for those ranked in the next 50 (Utah State, Michigan, and Fresno State based on 2014 rankings). If the actual numbers turn out anywhere close to these projections, we should see another solid defensive unit for the Cougars in 2015.

And if you combine a much stiffer defense with the powerful potential of the 2015 BYU offense, it’s hard to put a ceiling on the possibilities for 2015.


  1. Dereck Smith

    May 15, 2015 at 7:52 am

    Bronco’s 2 biggest strengths as a DC are in my opinion

    1) Great Buy in and intensity form the players. This is most evident from the Jaime Hill take over. The tone and effectiveness of the defense was literally changed overnight (or at least overweek).

    2) Covering/compensating for weaknesses. A great example of this is in 2013 when BYU basically lost its top projected 6 corners to either injury or million dollar baseball signing bonuses. They started a walk on safety at one corner spot, and at the other a guy who hadn’t seen the field in almost 2 years whose only offer was from BYU and that happened months after national signing day and only occurred because of all the injuries at the position. The result was a defense that was ranked 7th in the country in yards allowed per pass attempt.

    The issue with this years defense is that there is not a lot of experience and talent. You have some talented outside linbackers, but they have almost no experience. You have some experienced defensive linemen, but minus Kaufusi they managed only 1.5 sacks last year.

    Depth is also an issue. I like Takinaki and Nakua at safety, but after them there is no experience and apparently only marginal talent. And of course Nakua is going to miss at least the first 2 games next year.

    The middle linebacker position is a mess. That is scary because of how important that position is to a Bronco defense.

    I think that this could be Bronco’s worse defense in large part due to the personnel he has at the moment. Honestly, if he can get them to be statistically average this year, he will have done a good job. Of course if the offense stays healthy, an Average defense could be enough to win, or at least challenge for, every game on their schedule.

  2. Dereck Smith

    May 15, 2015 at 8:52 am

    The trouble with Hill and Howell comparisons is that they only coached one defense. Hill had a talented defense, so his numbers compared too all other defenses look pretty good. But to see the real difference, I look at the before at after stats from that 2010 season.

    Yards per pass attempt
    Hill lead defense: 7.78 ypa good for 109th in the country (projecting against 2014 stats)
    Bronco lead defense: 5.79 ypa (7th)

    Yards Per Rush Attempt
    Hill lead defense: 5.01 ypa (101st)
    Bronco lead defense: 2.63 (1st)

    Points allowed per game
    Hill lead defense: 28.8 ppg (81st)
    Bronco lead defense: 16.1 (2nd)

    That is a ridiculous discrepancy especially since it was the same players and the switch happened in the middle of the season.

    Now admittedly Hill’s schedule was more difficult, but not drastically so and not nearly enough to change an elite defense into a bottom feeder or Visa Versa.