Writers of Pro Football Prospectus 2008

2015 NCAA S&P+ RATINGS, DEFENSE

through games of 9/1/15

S&P+ Ratings will be updated beginning after Week 1 of the 2015 college football season.

The S&P+ Ratings are a college football ratings system derived from the play-by-play data of all 800+ of a season's FBS college football games (and 140,000+ plays). S&P+ ratings are based around the core concepts of the Five Factors: efficiency, explosiveness, field position, finishing drives, and turnovers.

While turnovers do not play a significant role in offensive and defensive ratings, here are the factors that do:

  • Success Rate: A common Football Outsiders tool used to measure efficiency by determining whether every play of a given game was successful or not. The terms of success in college football: 50 percent of necessary yardage on first down, 70 percent on second down, and 100 percent on third and fourth down.
  • IsoPPP: An explosiveness measure derived from determining the equivalent point value of every yard line (based on the expected number of points an offense could expect to score from that yard line) and, therefore, every play of a given game. IsoPPP looks at only the per-play value of a team's successful plays (as defined by the Success Rate definition above); its goal is to separate the explosiveness component from the efficiency component altogether. For more information about IsoPPP, click here.
  • Redzone S&P+: This measures drive-finishing ability by looking at the success rate and IsoPPP measures for only plays that come after a first down inside the opponent's 40-yard line. Coaches start adjusting their play-calling for a shrinking field closer to the 40 than the 20, and there is more separation between good and bad offenses if you look at plays in this range instead of plays inside the 20-yard line (as the redzone is commonly defined).
  • FP+: This is an opponent-adjusted measure of your ability to create field position advantages. This is based on drive data instead of per-play data. For an offense, it looks at field position you create for your defense (with help from special teams, which is not yet stripped out of these numbers); for a defense, it looks at the opposite.
  • Opponent adjustments: Each team's output for a given category (Success Rate, IsoPPP, and split stats like rushing, passing, redzone, standard downs, passing downs, etc.) is compared to the expected output based upon their opponents. This is a schedule-based adjustment designed to reward tougher schedules and punish weaker ones. In the tables below, the "+" designation is for measures that are adjusted for opponent.
  • Garbage time adjustments: The S&P+ figures used in the tables below only look at the plays that took place while a game was deemed competitive. Garbage-time plays and possessions have been filtered out of the calculations. The criteria for "garbage time" are as follows: a game is not within 28 points in the first quarter, 24 points in the second quarter, 21 points in the third quarter, or 16 points in the fourth quarter.

Passing Downs are defined as:

  • second down with 8 or more yards to go
  • third or fourth down with 5 or more yards to go

All other downs are Standard Downs.

Overall offensive and defensive S&P+ ratings are communicated as adjusted scoring averages (points per game). Situational 'plus' ratings -- Rushing S&P+, Success Rate+, FP+, etc. -- are still delivered on a scale in which 100.0 is the national average, above 100 is good (offense or defense) and below 100 is bad.

Please note that in the split of rushing and passing S&P+, sacks are counted as passes, as in NFL data, and not runs as in official NCAA totals.

The first table below offers situational stats -- rushing, passing, standard downs (SD), and passing downs (PD) -- and a team's opponent-adjusted Success Rate and IsoPPP measures. The second table offers more Five Factors stats (FP+, Redzone S&P+), unadjusted Success Rate and IsoPPP measures, and three Havoc stats. Havoc Rate is a team's total tackles for loss, passes defensed, and forced fumbles divided by total plays. (Learn more here.) Each's team's Havoc Rate and numbers specific to the front seven and secondary are shared below.