Analytics, Basic Stats, and Recent Historic Context: The ABC’s of Penn State Football – The 2021 Defense Retrospective

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Introduction

Cue Sarah McLachlan singing, “I Will Remember You” as we watch Brent Pry walk out the door towards Blacksburg. An Altoona man with an Alabama accent, Pry orchestrated steady, reliable and occasionally dominant defensive units throughout his six-season reign as DC in Happy Valley. That level of consistency on defense was the Yin to the offense’s erratic Yang – explosive in 2017, plodding in 2020, one-dimensional in 2021. For his final act wearing blue and white, Pry and his talent-rich defense compiled one of the best statistical defensive performances in recent history…which we’re about to explore.

Our format for this Penn State Defense Year-in-Review will mirror what we did earlier this week with the offense: basic stats first, more complicated advanced stats second. Unlike the offense blog post from Monday, however, the stats/numbers in this defense article won’t need a NSFW warning. In fact, you might gain a newfound appreciation for Pry after reading this one.

As always – all data herein is only against FBS competition (sorry Villanova) unless otherwise noted.

Yardage Production

Penn State’s yards allowed per game (YPGA) totals reinforce the oft-repeated “Bend But Don’t Break” narrative media and fans parroted all season long. In this metric, the 2021 Penn State defense was good but not great. Penn State allowed 360 YPGA in 2021, good for 40^th in the nation. That average was 31 yards worse than 2020, which initially seems a bit surprising until you remember all the short fields last year’s Nittany Lions had to defend off of turnovers. In fact, only two other Pry defenses surrendered more yards per game than this 2021 group – the Big Ten champion 2016 team (367.9 YPGA) and the 11-win 2019 team (363.3 YPGA).

Now, ranking 40^th nationally in Yards Allowed Per Game is certainly respectable, but consider this: the 2021 Penn State defense was on the field for 75.4 plays per game. That’s the 10^th most played defended per game in FBS and nearly 9 plays more than the national average. Some of this is a function of the clunky 2021 offense not sustaining drives. Therefore, Yards Allowed Per Game probably isn’t the best measuring stick for the 2021 Penn State defense.

But Yards Allowed Per Play (YPP-A) certainly is.

Penn State’s defense held opponents to 4.8 yards per play this season. That’s the 8^th best mark in the country, trailing the likes of Wisconsin, Georgia, Clemson and a handful of others.The 4.8 (4.77 precisely) yards allowed is nearly a full yard better than the FBS average of 5.73. So, yeah, Penn State really thrived in this statistical category. In fact, the chart below shows Pry’s defenses have always been at least a half-yard better than FBS average throughout his tenure as Penn State DC.

Moving on…

Penn State’s rush defense was mostly stellar sans two games. Can you guess which ones? Yep, Illinois and Arkansas. The orange (Illinois) and red (Arkansas) dots in the upper right corner of the graph below represent two sore points for the defense in 2021. Illinois lined up 8 offensive linemen and bullied the unprepared PSU defense. Arkansas used its man-sized QB on zone reads and eventually wore down the opt-out plagued Lions. This ends the negative portion of the section. If you exclude these two games, the defense allowed an average of 115 rushing yards per game (including Villanova) which would be in line with some of the best seasons in the recent past.

In terms of passing yards allowed, the 2021 unit was the 2^nd best of the Pry era allowing slightly under 200 YPG. In three contests – Illinois (38), Rutgers (93), and Arkansas (98) – Penn State kept its opponent from reaching tripe figures through the air. The fact that 2 of those 3 occurrences ended with an L is funny (in a very sad way). Since 2014 the Penn State defense has allowed fewer than 100 passing yards 14 times. They are 10-4 with the other two losses being 2014 OSU and 2016 Pitt.

As I mentioned above, an average defense gives up 5.7 yards-per-play. The Penn State defense allowed an average number or greater 3 times this year: Ohio State, Michigan State, and Arkansas. Pry’s Lions were a very consistent defense. So that you don’t have to look it up, that orange dot at the top of the 2019 season was Minnesota.

Scoring

Throughout his tenure, Pry’s defenses have done an above-average job keeping points off the scoreboard. 2021 was no exception. This year’s Lions finished as the 5^th best defense when it comes to points allowed, 17.3 PPG (excluding FCS). Pry also had Top 10 scoring defenses in 2017 and 2019, and a Top 20 scoring defense in 2018. Penn State won 11 games in the previous two seasons Pry’s defenses finished in the Top 10 in scoring. This year, they limped to a 7-6 record…which is hard to fathom and tough to swallow.

Looking at points allowed on a game-by-game basis below, we see that the floor of the defense (33 points allowed against Ohio State) was the best under Franklin. Every other year since 2016 there was a game or two where the defense leaked 35 points or more, but not in 2021. Considering Penn State played an offense loaded with first-round WRs and a Heisman finalist (Ohio State) and another with the Doak Walker winner (Michigan State) holding all opponents under 5 TDs this season was a fairly impressive feat.

One of the big issues with the COVID-shortened 2020 season was Penn State’s inability to keep opponents from scoring points inside the Red Zone. You’ll remember if you read the Offense Year-in-Review post that the 2020 Penn State offense had the same problem but in reverse – they couldn’t score. Unlike the 2021 offense – which once again struggled to convert Red Zone trips into TDs – the 2021 defense displayed incredible improvement versus 2020 and was the 3^rd best defense in the country in Red Zone points allowed per trip.

Penn State finished 79^th nationally in red zone attempts allowed per game – bend don’t break. When you combine the two metrics (points per RZ attempt x RZ attempts per game) the Lions were the 14^th best team at total RZ points per game allowed. Against the 2021 Penn State defense, opponents could march down field, but it usually didn’t mean much in the end.

 Finally, why don’t we look at points scored outside of the Red Zone (Not sure how to abbreviate this one. PORZ maybe? Suggestions welcome). Again, I view this stat as a good proxy for a defense’s ability to limit explosive plays. An average FBS defense allows 10 PORZ per game. That means they give up one TD and one FG on average from beyond the 20-yard line. If you have paid attention to Big Ten football in the last decade, you’ve heard about how Iowa’s defensive game plan is to limit big plays. This year, they averaged 4.0 PORZ per game which was the 4^th best in the country. The leader was Arizona State (3.6 PORZ/game) followed by Georgia (3.7 PORZ/game). The Nittany Lions finished 6^th in FBS (4.1 PORZ/game). Bend don’t break.

Advanced Stats

Let’s start the Advanced Stats portion of this Year-in-Review with Penn State’s Havoc rate. Unfortunately, 2021 continued one of the more negative trends attached to recent Penn State defenses as Havoc rate once again declined. This year’s 13.3% Havoc rate was below FBS average – the first time that’s ever happened under Pry. Again, for the 50^th time, Havoc comes from Bill Connelly. My slightly modified Havoc metric is the % of plays a defense causes a turnover, TFL, or sack.

The first three years under Pry, the Lions were near the top of FBS with a Havoc rate of 17-18%. From 2019-2021, those Havoc numbers have declined nearly 2%/year. The main culprit In 2021 was Penn State’s inability to register sacks and TFLs. This year, Penn State averaged 8.3 Sacks+TFLs per game – well below the peak from previous seasons. This is one area where we will expect substantial improvement with Manny Diaz as DC in 2022. On the bright side, 2021 saw the defense average 1.7 takeaways per game which was up considerably from 1.0 in 2020. As we’ve said before, we’ll always take a turnover over a couple of sacks or TFLs.

Next, Explosivity. We measure Explosivity by multiplying points and yards (Yard*Point = overall productivity) and then dividing by 100 plays. So, if a defense prevents teams from scoring lots of points and generating lots of yards in a small number of plays, they are limiting Explosivity. Like the PORZ stat above, the 2021 installation of Penn State’s defense was fantastic in this metric. They were 6^th best in the country behind Georgia, Wisconsin, Clemson, Cincinnati, and Texas A&M – very good defensive company.

Before we finish with the overall effectiveness measure, I want to look at a scatter plot of yardage efficiency (yards per drive) and scoring efficiency (points per drive) allowed. The plot below shows every FBS team’s performance since 2009 as a gray dot and the gray line indicates the relationship between yards allowed and points allowed. Below the line means a team allows fewer points than would be expected for a given number of yards and vice versa. Values that are down and to the left are generally better. Brent Pry has commanded the defense since 2016 and, except for that season and 2020, his teams have held opponent scoring below expectation. In fact, if we look at points-per-drive allowed, out of all the 1640 gray dots on the graph, Pry’s defenses rank: 46^th (2017), 89^th (2019), 101^st (2021), 141^st (2018), 471^st (2016), 762^nd (2020). With one exception, he’s placed every unit in the top-third of FBS defense since 2009.

Finally, we have our Defensive Effectiveness (DE) metric. It reinforces the consistency of Brent Pry’s defenses while at Penn State and confirms that the 2020 season was a statistical outlier.

Conclusion

Writing this blog and compiling all the numbers that went into it was bittersweet. Sure, it was great to put together charts confirming Penn State’s place as one of college football’s elite defenses this season. At the same time, it was frustrating doing so knowing this team, with this top-shelf defense, lost 6 of its final 8 games. The defense did its job — always put the team in a position to win games. They limited scoring, generated enough turnovers, and made opposing OC’s lives miserable. We now bid adieu to our DC of the past six seasons, Brent Pry, and welcome Manny Diaz who brings his own established track record of defensive excellence. We’ll dive into the Analytics and Advanced Stats of Diaz’s defenses when spring practice rolls around.