Friend of the program Bryan Frye is back for another guest post. As regular readers know, Bryan operates his own fantastic site, http://www.thegridfe.com. You can view all of Bryan’s guest posts here, and follow him on twitter @LaverneusDingle.
For some time, I have wanted to create a new metric that used elements from Total Adjusted Yards (TAY) in order to quantify a team’s production on each drive. Past work from both Chase and Brian Burke has given us insight into the value of touchdowns, interceptions, fumbles, and first downs, translated into yards. This work has been fundamental in the development of stats like Adjusted Net Yards per Attempt, Adjusted Rushing Yards, Adjusted Catch Yards, and TAY.
Those metrics have given us valuable insight regarding statistical measurement of individual player performance. I’ve also used TAY to measure the output of offenses and defenses.
However, I wanted to attach generic values to every way a drive can end.1 This is not a rigorous study, and it is meant to be a starting point for future research rather than a conclusive formula to govern the way anyone interprets on-field action.
With that in mind, I’ll briefly cover the generic yardage values for various drive outcomes.
First Down: Based on a 2014 study by Brian Burke, and accepted as the value in both Adjusted Rushing and Adjusted Receiving statistics, a first down is worth 9 yards. First downs are not yet included in ADY, but their value is an important part of other variables.
Interception: Based on work from John Carroll and Pete Palmer in the influential book, The Hidden Game of Football, and still used as the generic yardage value of a pick, an interception is worth -45 yards. The primary objection to this number is that it is based on numbers from the 1980s and is somewhat dated. Logically, the fact that most punts net about 35-40 yards, and a first down is worth about 9 yards, means a roughly 45 yard penalty makes sense. However, given the increased likelihood of an opponent drive ending in a score in 2015 is higher than it was in 1988, one could argue that the penalty is not severe enough.2 For the time being, I am sticking with the status quo.
Fumble: Based on Chase’s 2014 study, the penalty for a fumble should be roughly five yards more severe than the penalty for an interception. It is not perfectly clear that the value for an interception should still be -45, but because we are using that as the accepted value, a lost fumble is worth -50 yards. When using fumble values in ARY and TAY, I use -25 yards, given a roughly 50/50 chance at recovery. However, because a lost fumble is the only type of fumble that will end a drive (and still be marked as a fumble in the play by play data), it makes sense to use the full value for team drives.
Field Goal: Here, I did some simple calculations before adding a subjective change. Research by Brian Burke suggests that kicking the ball off to an opponent is worth about -0.7 points, meaning you must account for that when crediting scoring plays. A touchdown and field goal are, thus, really worth about 6.3 and 2.3 points. Since we’re using 20 yards as the generic value for touchdowns, the simplest way to give value for field goals is to use third grade math: 20 yards / 6.3 points is 3.2 y/p; 3.2 * 2.3 is 7.3 (numbers off due to rounding). After arriving at 7.3, I made the subjective decision to add 1.7 yards to make a field goal at least equal to a first down, or 9 yards.
Punt: The opportunity cost of a punt is a first down. Because we’ve already established that a first down is worth nine generic yards, the value I’m using for a punt is -9 yards.
Downs: This one is pretty simple. A turnover on downs means a team gave the ball to the opponent with the opportunity cost being a punt. Because punts net around 35 yards, the penalty for a turnover on downs is roughly -35 yards.
Missed Field Goal: A missed field goal is worth the points from a field goal plus the difference in opponent field position after the average missed field goal and the average kickoff. I didn’t have time to run all the numbers through years of play by play, so I chose to adopt an intuitive solution for this initial draft of the formula. The average team drive after each kickoff starts at the own 22 yard line. The average missed field goal attempt (that isn’t blocked) occurs around the 29 yard line. Add in the standard seven yards for the snap and hold, and we’re looking at an average opponent starting field position at the 36 yard line (a 14 yard difference in field position). The opportunity cost is the value of a field goal, so 9 yards. When we add the 14 and 9 yard costs to the value of a turnover on downs, we get a 58 yard penalty. Subjectively, I think this is too harsh, so I lowered the value to -50 yards.
Blocked Field Goal: Given that blocked field goals are another type of missed field goal, -50 yards will be our starting point. Most blocks happen at the line of scrimmage and are not returned by the defense. However, the blocks that are returned tend to go pretty far and often see defenders run unencumbered into the endzone. Given an average return of about 8 yards and the threat of a score,-60 yards seems like a reasonable penalty.
Blocked Punt: A blocked punt means three things. First, the punting team has forfeited the average 35 net yards of a normal punt. Second, they effectively suffered a fumble about twelve yards behind the line of scrimmage. Third, blocked punts that don’t travel past the line of scrimmage are often returned for uncontested scores. These are not common occurrences, so I didn’t put in the level of work for this initial project that I hope to put in later. For now, I’ll use a penalty of -60 yards for blocked punts.
Safety: Remember that a touchdown and a field goal aren’t really worth exactly 7 and 3 points, given that the result of both is that the scoring team gives the ball back to the opponent with the chance to reciprocate. From an expected points perspective, they are really worth about 6.3 and 2.3 points. Conversely, a safety is actually worth more than the points awarded, because the scoring team also gets the privilege of a brand new possession. When we account for the fact that a safety earns a team two points and gives them the ball, on average, sixty yards from the endzone, a safety may be worth up to four expected points. This is where I got a bit lazy. To find the value for a safety, as expressed in generic yards, I divided the 6.3 EP for a TD into the 20 yard bonus, coming to 3.2. Then I multiplied by four (the EP for a safety) and got 12.7. I decided to round to 13 yards for simplicity’s sake.
After coming up with some initial values for all these events, we can add the values to the actual yards gained on each drive to come up with a metric I will call Adjusted Drive Yards (ADY).
Adjusted Drive Yards
The table below contains Adjusted Drive Yards data for each team’s offense, defense, and overall performance. Read it thus: The Arizona Cardinals had 170 drives and gained 6059 ADY, a rate of 35.6 per drive. Their defense saw 180 drives and allowed 3319 ADY, a rate of 18.4 per drive. Overall, they gained 2740 more ADY than they allowed, and their per drive differential was 17.2, tops in the NFL.
Using the values from the first draft of the ADY formula puts NFC West rivals Arizona and Seattle at the top of the offensive ratings. The Patriots rate highly as well, as do the Saints – a team carried to a 7-9 record with perhaps the worst defense in modern history.
The only real surprise here may be the Giants ranking so high and the Panthers ranking so low (at least, low for the top scoring team in the league). One reason the Panthers rate relatively low is that their defense and special teams often gave them short fields and eliminated the need for long drives.
The Giants place near the top takes a bit more explaining, although it isn’t really complicated. On a per-drive basis, they were better than average at avoiding blocked punts, turnovers on downs, fumbling, missing field goals, allowing blocked kicks, and ceding safeties. They were better than average at making field goals and scoring touchdowns. They only area where they were worse than average was interception rate, where their 7.78% was slightly inferior to the league average 7.64%. Put all those things together, and you have a shockingly high rated offense.
Defensively, the Super Bowl participants rated one and two, well ahead of the third rated Texans. Nine of the top ten defenses participated in the postseason, while the non-playoff Jets once again suffered the unfortunate fate of playing in the same division as Tom Brady and Bill Belichick.
Similar to the Saints’ stellar offense being fettered by their awful defense, the Rams’ sturdy defense was unable to overcome ineptitude on the other side of the ball. Jeff Fisher hasn’t produced a worthwhile offense since the days of Steve McNair, and 2016 doesn’t look to be much different.
Sorting by differential shows that the top three rated teams in the league played in the NFC. So, naturally, the eighth rated AFC Champion Broncos won the title. This stat comes pretty close to the famous eye test, with all twelve playoff teams ranking in the top thirteen. Once again, the bad luck Jets are the highest rated team left out in the cold.
I don’t want to send too much time pointing out every little pattern or oddity I see. I’d rather hear outside opinions, so leave your thoughts in the comments.
- With the exception of kneel down drives to end halves or games, as those don’t demonstrate an offense’s (or defense’s) ability to actually play the game. [↩]
- Indeed, Brian Burke has argued that a modern interception is worth about -60 yards. However, Burke did state in a personal communication that this is only applicable to interceptions thrown on first down and that the generic value should be close to 50 [↩]