Deep Stats Defensive Review: Part 1

By Craig Fritz on June 20, 2018 at 3:05 pm
Penn State Defensive Coordinator Brent Pry
Adriana Lacy - Roar Lions Roar
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When you've long been known for your defensive football, having a top-20 unit is the expectation, not the exception. For the Nittany Lions, Brent Pry has directed top-20 units according to S&P+ in both of his seasons as defensive coordinator. That isn't to say everything is was great, far from it, but his units graded out as border-line elite in 2016 and 2017. Today we'll look at the biggest year-over-year improvements for Pry's squad (increase of more than 15 spots nationally).

For those reading for the first time, S&P+ is an advanced statistical system designed by Bill Connelly of Football Study Hall and SBNation. We already went through the biggest improvements and declines by the Penn State offense last year. This handy glossary will help us decipher the inner workings of Bill C.'s system.

overall 2016 rank 2017 rank difference
explosiveness 51 24 27
efficiency 36 12 24
field position 48 6 42
  • Nothing but improvement overall for the defense. Limiting Explosiveness went from mediocre to good. Stopping Efficiency went from good to great. These are things metrics that show limited scoring opportunities for the opponent, and quick returns of possession to the offense.
  • Field Position jumped too. You'll note from the glossary that a defense is measured by a team's offensive starting field position. This means that the 2017 defense was among the nation's best at giving Trace McSorley and company a short field to go score. Certainly a huge improvement over 2016.
rushing  2016 rank 2017 rank difference
rushing success rate 30 15 15
rushing isoppp 63 25 38
opportunity rate 43 20 23
  • Again we see a good stat move into the elite category with Rushing Success Rate. This means that Pry's unit was very good at preventing rushing plays from gaining 50 percent of necessary yardage on first down, 70 percent on second down, and 100 percent on third and fourth down.
  • Rushing IsoPPP, which recall is limiting an offense from being consistently successful, and when they were successful, limiting their potency (big plays), made a move from mediocre to good. The defense really clamped down on explosive run plays throughout the season.
  • With another move from ho-hum to good, Pry's defense excelled in limiting opponents' Opportunity Rate, or the number of times a foe's offensive line was able to create at least five yards of gain for their running back.
passing 2016 rank 2017 rank difference
Passing s&p+ 48 13 35
passing success rate 54 23 31
  • The major move in defensive Passing S&P+ can be attributed to a few things. An all-senior secondary, a more effective pass rush, fewer quality quarterbacks on the schedule. It's a measure that Pry will want to repeat, and should have the tools to do so. 
  • Just like against the run, the defense was able to step up its game in preventing successful plays across the down/distance spectrum. This was a welcome improvement.
standard downs 2016 rank 2017 rank difference
standard down s&P+ 34 19 15
Standard down isoppp 46 31 15
  • Both of these measures trend to the positive in normal football situations. Remember Standard Downs are first downs, second-and-7 or fewer, and third/fourth-and-4 or fewer. These are the downs in which the offense could conceivably either run or pass and therefore has an overall advantage over the defense. According to Bill C., college offenses operate on standard downs about 60 percent of the time. That means good defensive rankings on standard downs shows the defense is forcing offenses off-schedule and limiting big plays.
passing downs 2016 rank 2017 rank difference
Passing down S&P+ 52 20 32
pass down success rate 54 14 40
Pass down isoppp 41 11 30
  • There's that senior-laden secondary again. Extremely impressive jumps compared to the previous year for Passing Downs, which are second-and-8 or more and third/fourth-and-5 or more. These are downs in which passing is easily the most likely option for gaining the necessary yardage, and defenses hold the upper hand. Offenses typically throw about two-thirds of the time on passing downs.
  • Consider that defenses which are solid-to-good on standard downs are likely to force a ton of passing down situations. So Penn State forced more one-dimensionalism from its opponents by creating tough sledding on normal down/distance situations and then attacking during obvious passing situations.
  • The Passing Down IsoPPP jump is awesome. The 2017 defense rarely got burned by big plays, which is an extension of the great overall improvement in defensive explosiveness. 
situational 2016 rank 2017 rank difference
1st quarter s&p+ 61 21 40
2nd quarter s&p+ 48 12 36
2nd down s&P+ 51 6 45
  • Just like the offense, it seems the defense got its act in gear right off the bat in games. These first-half improvements are absolutely awesome. Talk about setting the tone early in a game.
  • That huge jump in 2nd Down S&P+ is something to behold. Pry's calls on 2nd down came up aces all year. It was BY FAR the defense's most effective down.
  • All of these situational improvements are among the largest improvements for Pry's unit over 2016. 
havoc 2016 rank 2017 rank difference
overall 30 11 19
DB havoc 78 8 70
PD to inc 67 27 40
  • This is one of my favorite sections of S&P+ because it's one of the few defense-only metrics in the system. Havoc is defined as the percentage of plays in which a defense either recorded a tackle for loss, forced a fumble, or defensed a pass (intercepted or broken up). The Nittany Lions went from good to elite in overall havoc in 2017, and man it was fun to watch.
  • Looong whistling...the DB havoc improvement is absolutely insane. There's a ton of talent left in the secondary, but man, that number is going to be tough to replicate in 2018.
  • PD to INC is another fun one. It looks at the percentage of an opponent's incomplete passes that were either intercepted or broke up. According to Bill C., this isn't necessarily a quality stat, just a look at general aggressiveness levels. So with a veteran secondary, Pry took a lot of chances, and they mostly paid off.

This is the third post in a series looking at the year-over-year improvements or declines in performance across the Nittany Lion offense and defense. Next up we'll look at the areas of largest decline for the defense. [Part 1 - Offensive Improvement] [Part 2 - Offensive Decline] [Part 4 - Defensive Decline]

Hit up the comments to discuss the ins-and-outs of Penn State's S&P+ and where you think we can expect defensive improvement in 2018!

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