THINGS TO KNOW FOR 2015
New S&P+ ratings
Because deadlines are converging all at once, I haven't yet updated the S&P+, Off. S&P+, and Def. S&P+ pages to reflect this, but I have completed a rather significant redesign of the S&P+ ratings, how they're derived, and how they're communicated. I will write more about this when they are actually posted.
Here's what that means for the 2015 college football preview series:
- Percentiles. One of the biggest changes I made within the S&P+ ratings was adherence to normal distributions. College football straps itself pretty closely to the bell curve -- even more than I realized until recently -- and because of that, I found it a pretty good idea to communicate where teams fall on a bell curve more frequently. So you'll see "average percentile performance" emerging as a primary way for me to talk about teams' previous performances. Because of everyone's history with standardized tests, this is a pretty easy concept to understand and communicate.
- Win Expectancy. Also within the "last year's schedule and results" section, you'll find me using what I'm calling here "Win Expectancy." This communicates how frequently a team would have won a specific game given that game's primary stats. It is intended to say "Given your success rates, big plays, field position components, turnovers, etc., you could have expected to win this game X% of the time." It has nothing to do with pre-game projections or opponent adjustments.
- Second-order wins. Using those Win Expectancy numbers for the entire season, you get a pretty good idea for how many games a team could have expected to win. As I mentioned here, "[second-order wins] basically say that playing the way you did, against the opponents you played, you would usually end up with a record of X, and it compares it to your actual record, Y. If one is too far from the other, you're probably going to see some regression (or progression, as the case may be) to the mean." In the preview series, you can find Second-order wins in the "2015 Schedule & Projection Factors" section.
- S&P+ ratings = adjusted points per game. Instead of basing everything on a scale that equates a 100.0 rating to the national average, I thought it would be interesting to apply it to the scoring curve instead. What that means is, your Off. S&P+ rating is now presented as an adjusted scoring average. (This will be explained in more detail when I get the S&P+ ratings pages updated.)
247 Composite Ratings
I am including both Rivals and 247 Composite ratings within each player's line in the season previews this year. I am sharing the actual decimal rating instead of the star rating, but the general gist is that anyone above a 0.9000 is a four- or five-star, anyone above 0.8000 is a three-star, etc.
Adj. Line Yards
An opponent-adjusted version of the line measure derived from the formula found here. The idea is to divvy credit for a given rush between both the runner and the blockers.
Part of the offensive footprint, this takes into account both the number of plays a team attempts and the type of play. Since passes, on average, take up less time (thanks to the fact that 30-50 percent of them are incomplete and stop the clock), pass-heavy offenses are prone to run more plays, therefore limiting the effectiveness of a general plays-per-game measure. Adj. Pace takes a team's run-pass ratio into account.
Adj. Points and Scoring Margin
A look at how a team would have performed in a given week if playing a perfectly average team, with a somewhat average number of breaks and turnovers. It takes into account the factors that go into winning a given game (not simply the end result) and adjusts for the quality of opponent.
A derivation of Adj. Points, Adj. Record is based on single-game S&P+ performances. This is the record a team would have had playing a perfectly average team, with a perfectly average number of breaks, in each week of the season. Adj. Record gives you a different way to visualize the impact of both team consistency and schedule strength. Note: since both teams in a given game are being compared to a baseline average (instead of each other), it is conceivable that both teams could end up with an adjusted win or loss.
Adj. Sack Rate
An opponent-adjusted measure of sack rates.
Adj. TO Margin
What a team's turnover margin would have been if they had recovered exactly 50 percent of all the fumbles that occurred in their games, and if the INTs-to-PDs for both teams was equal to the national average, which is generally around 21-22 percent. If there is a huge difference between TO Margin and Adj. TO Margin (in other words, if fumbles, dropped interceptions, or other lucky/unlucky bounces were the main source of a good/bad TO margin), that suggests that a team's luck was particularly good or bad and might even out the next season.
See the Five Factors section.
Part of the defensive footprint, this is a comparison of a team's Def. Success Rate (efficiency) to its Def. PPP (explosiveness). The higher the number, the higher percentage of a team's overall S&P was made up by success rate, i.e. the more willing a team was to sacrifice efficiency to prevent big plays. (The lower the number, the more likely a team was to take aggressive risks.)
Covariance is a statistical tool that provides a measure of the strength of the correlation between two or more sets of random variates. For these purposes, it is used to compare a team's performance (using opponent-adjusted Adj. Score) to the quality of the opponent at hand. Some teams play their best games against their worst opponents, and some teams do the opposite. For more, go here. (NOTE: This is a concept I no longer use in the offseason preview series. It is interesting, but I'm not sure how useful it can be with 12-14 data points.)
The official college football ratings of record at Football Outsiders. F/+ is a combination of the Brian Fremeau's Fremeau Efficiency Index (FEI) and my S&P+.
The Five Factors are the basis for the new S&P+ ratings. They stem from the work done in this post.
But over time, I've come to realize that the sport comes down to five basic things, four of which you can mostly control. You make more big plays than your opponent, you stay on schedule, you tilt the field, you finish drives, and you fall on the ball. Explosiveness, efficiency, field position, finishing drives, and turnovers are the five factors to winning football games.
- If you win the explosiveness battle (using PPP), you win 86 percent of the time.
- If you win the efficiency battle (using Success Rate), you win 83 percent of the time.
- If you win the drive-finishing battle (using points per trip inside the 40), you win 75 percent of the time.
- If you win the field position battle (using average starting field position), you win 72 percent of the time.
- If you win the turnover battle (using turnover margin), you win 73 percent of the time.
This is from 2013 college football game data. It's very, very similar from year to year.
These are good odds. And they speak to the fundamentals of football itself. You want to be efficient when you've got the ball, because if you fall behind schedule and into passing downs, you're far less likely to make a good play. You want to eat up chunks of yardage with big plays, because big plays mean both points and fewer opportunities to make mistakes. When you get the opportunity to score, you want to score. And when you give the ball back to your opponent, you want to give them to have to go as far as possible.
Aside from their impact on the new S&P+ ratings, the Five Factors will be accounted for in the 2015 season previews in 10 ways -- five adjusted for opponent, five not, and all interrelated:
- Efficiency. Success Rate (unadjusted) and Success Rate+ (adjusted). As defined above, success rates examine your efficiency and consistency in staying on schedule and putting yourself in position to move the chains.
- Explosiveness. IsoPPP (unadjusted) and IsoPPP+ (adjusted). IsoPPP is the Equivalent Points Per Play (PPP) average on only successful plays. This allows us to look at offense in two steps: How consistently successful were you, and when you were successful, how potent were you?
- Field Position. Average Starting Field Position (unadjusted) and FP+ (adjusted). This is mostly self-explanatory, with one important note: An offense is measured by its defense's starting field position, and vice versa. Special teams obviously play a large role in field position, but so do the effectiveness of your offense and defense. So in the team profiles, you'll find Defensive Starting FP in the offensive section and Offensive Starting FP in the defensive section.
- Finishing Drives. Points Per Trip Inside the 40 (unadjusted) and Redzone S&P+ (adjusted). Also mostly self-explanatory. These measures look not at how frequently you create scoring opportunities, but how you finish the ones you create. And yes, for the purposes of these stats, the "red zone" starts at the 40, not the 20.
- Turnovers. Using both Turnover Margin and Adjusted Turnover Margin (as defined above), we can take a look at both how many turnovers you should have committed (on offense) or forced (on defense) and how many you actually did. This tells us a little bit about quality and a lot about the Turnovers Luck idea defined above.
See the Five Factors section.
Fremeau Efficiency Index (FEI)
FEI considers each of the nearly 20,000 possessions every season in major college football. All drives are filtered to eliminate first-half clock-kills and end-of-game garbage drives and scores. A scoring rate analysis of the remaining possessions then determines the baseline possession efficiency expectations against which each team is measured. A team is rewarded for playing well against good teams, win or lose, and is punished more severely for playing poorly against bad teams than it is rewarded for playing well against bad teams. For more, go here.
Garbage Time %Run
This personality stat looks at how an offense operated when a game was out of reach -- i.e. not within 28 points in the first quarter, 24 in the second, 21 in the third, or 16 in the fourth -- either when a team was winning or losing.
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). If QB hurries were a reliable stat (at the college level, there is far too much inconsistency in how they are recorded), they would be included here, too.
The portion of a given run that is credit only to the running back; after a certain number of yards, the line has done its job, and most of the rest of the run will be determined by the running back himself. For more information, start here. An important note: a player's per-carry highlight yardage is now calculated as follows: Highlight Yards divided by Opportunities. In this case, Opportunities mean only the carries in which the offensive line "did its job," i.e. carries that went at least five yards. With a different denominator, then, it is possible for a player's Highlight Yards per carry to be much higher than his overall yards per carry.
See the Five Factors section.
Need for Blitzes
Part of the defensive footprint, this generalized measure compares a team's standard downs sack rate to its passing downs sack rate. The lower the number, the more they were able to generate pressure on standard downs, and the less need for blitzes.
This is the percentage of carries in which the offensive line "does its job" and produces at least five yards of rushing for the runner. (Generally speaking, the first five yards are considered the line's responsibility, the next five are split evenly between the runner and the line, and anything over 10 yards is all on the runner.) See Highlight Yards and Adj. Line Yards for more information.
Second-and-8 or more, third-and-5 or more, or 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.
A defensive personality stat, this looks at the percentage of an opponent's incomplete passes that you either intercepted or broke up. This isn't necessarily a quality stat, just a look at general aggressiveness levels.
Points Per Trip inside the 40
See the Five Factors section.
Power Success Rate
As used in Football Outsiders' pro line stats, this is the percentage of runs on third or fourth down, two yards or less to go, that achieved a first down or touchdown. Also includes runs on first-and-goal or second-and-goal from the two-yard line or closer.
Points per play is an explosiveness measure derived from determining the 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. NOTE: As mentioned in the Five Factors section, PPP is being phased out in favor of IsoPPP, which looks only at the explosiveness of successful plays.
An opponent-adjusted version of PPP. As with most other "+" measures, it is built around a baseline of 100.0. Anything over 100.0 is better than average, anything below 100.0 is worse than average.
See the Five Factors section.
A college football ratings system designed by me and derived from the play-by-play and drive data of all 800+ of a season's FBS college football games (and 140,000+ plays). For more, go here.
First downs, second-and-7 or fewer, third-and-4 or fewer, and 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. Offenses typically run about 60 percent of the time on standard downs.
This is the percentage of runs where the runner is tackled at or behind the line of scrimmage. Since being stuffed is bad, offenses are ranked from stuffed least often (No. 1) to most often (No. 125); for defenses, the opposite is true.
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.
An opponent-adjusted version of Success Rate. As with most other "+" measures, it is built around a baseline of 100.0. Anything over 100.0 is better than average, anything below 100.0 is worse than average.
Presented in Points Per Game fashion, Turnovers Luck looks at the difference between a team's Turnover and Adj. TO Margins and, using the average point value of a turnover (~5.0 points), projects how many points a team gained or lost per game last season.