Every so often here on BTB we shine the light on some stats that don't get a lot of airtime in the majority of the media outlets that cover the NFL. Most recently, we looked at Passer Rating Differential, and a while back we looked at Adjusted Net Passing Yards per Attempt, or ANY/A. Today, I'd like to introduce you to a stat called Drive Success Rate.
At the core of every football game is the drive. The entire game is predicated on the ability of the offense to move the ball far enough to get into scoring position and ultimately to score points. The objective of the defense is to prevent exactly that.
One way of measuring a team's effectiveness of doing both is the Drive Success Rate (DSR), conveniently brought to us by Football Outsiders. DSR measures a team's ability to successfully move the ball or stop the opponent from moving the ball by measuring the percentage of down series that result in a first down or touchdown. Here's FO's own definition:
Drive Success Rate (or more precisely, series of downs success rate), or DSR, measures the likelihood that a team's offense will get another first down (or a touchdown, which the official NFL statisticians also count as a first down) in a given set of downs. And the equivalent defensive number measures how often a defense will allow another first down.
To my knowledge, FO don't publish the exact formula for how they arrive at their DSR numbers, but based on the results they publish, the formula should look like this:
(First Downs + Touchdowns) / (First Downs + Drives)
Note that the FO data is taken from the standard NFL drive chart, and as far as I can tell, their formula excludes End of Game or End of Half possessions that did not result in a first down (typically kneel-down situations), and also excludes turnovers on kick- or punt returns (in the NFL gamebooks these count as offensive drives with zero plays).
The Cowboys get the ball on their 20-yard line after a Bears kickoff. Murray runs left for an 11-yard gain and a first down. That's a success. After that, Romo connects with Ogletree on 2nd-and-7 for a 13-yard gain. Another first down and another success. On the next set of downs, the Cowboys convert a 3rd-and-7 on the 50-yard line with a 7-yard pass to Jason Witten. Yet another success on this drive. The next set of downs should bring the Cowboys within scoring distance, but on 3rd-and-7 on the Chicago 40, Romo is sacked for a loss of seven yards. The Cowboys punt the ball; that final series of downs was obviously not a successful.
In this example, the Cowboys had a Drive Success Rate of 75%: they got three first downs on four opportunities.
As a rule of thumb, the best offenses are those that move the ball down the field most effectively, the best defenses are those that prevent their opponents from moving down the field effectively. The best teams in the league are those that do both most effectively.
And the best way to measure a team's overall drive effectiveness is by looking at the Net Drive Success Rate: the difference between a team's offensive DSR and its defensive DSR. The Net DSR tells you how much more effective a team is at moving the ball relative to its opponents.
Here are the 2011 teams as ranked by Net DSR:
|Net Drive Success Rate, 2011
|Rank||Team||DSR Offense||DSR Defense||Net DSR||Rank||Team||DSR Offense||DSR Defense||Net DSR|
|Playoff teams highlighted in bold|
Note how almost all playoff teams appear on the left side of the table? That's no coincidence. The better your NET DSR, the higher your number of wins usually is. Conversely, the teams with the biggest negative differential had some of the lowest win totals last year.
In statistics, the relationship between two variables such as wins and Net DSR is called a correlation, and is measured by the correlation coefficient or "r²". The closer that number is to 1 or -1, the higher the correlation. R² between wins and Net DSR in 2011 was 0.67, a fairly high correlation, and one of the highest observed stat/wins correlations in the NFL.
Now for a little detour, just for fun. Here are some correlations with 2011 W/L records and a collection of other stats:
|Passer Rating Differential||0.80|
|Passer Rating Offense||0.62|
|Passing Yards OFF||0.34|
|Passer Rating Defense||0.31|
|Passing Yards DEF||0.08|
*ANY/A: Adjusted net passing yards per attempt = (Passing Yards + (Passing TDs)*20 - (INTs thrown)*45 - Sack Yards) / (Passing Attempts + Sacks)
*Y/A: Yards gained per pass attempt (Passing Yards / Passes Attempted).
*NY/A: Net yards gained per pass attempt, which is basically Y/A adjusted for sacks (Passing Yards - Sack Yards) / (Passes Attempted + Sacks).
For the Cowboys, 2012 has not started well, and many of the advanced metrics available to us suggest that with the way the Cowboys have played, they are actually lucky to have a 2-2 record. Of course, with two blowout games in which the Cowboys were outscored 61-25, that tends to happen.
The Cowboys are ranked 21st on offensive DSR and 12th on defense. Their Net DSR of -0.003 ranks them only 20th in the league. That happens when you rank among the top in the league in dropped passes (10), giveaways (11) and penalties (33). Add a middling 39.6% third down conversion rate and it should be no surprise that the Cowboys have not been particularly successful at moving the ball down the field on offense.
Just for your reference, the Cowboys are ranked 24th in points differential (-23), 23rd in passer rating differential (-12.6) and 22nd in ANY/A differential (-0.9). From here, really, things can only get better.