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Sunday, October 7, 2007

The Forward Lateral vs. Keepin' It on the Ground

This first half of Texas A&M's season has been primarily defined by a debate that sees coaches and players on one side and many fans and commentators on the other. The players' and coaches' position was spelled out by a post-game rant from quarterback Stephen McGee. After beating Fresno State is triple overtime, McGee fielded questions on the team's inability, or unwillingness, to throw the ball down field:
I'm so tired of hearing about that. When it comes down to it, we're a team. We're going to do whatever it takes to win. Today we did that. That's what it comes down to: getting the ball into the end zone. Offensively, we ran the ball every freakin' time, and they did not stop us. I wouldn't see us doing anything different. That's what we are about: getting the ball in the end zone.1
Getting the ball in the end zone is important, but A&M blew a 19 point lead at halftime and needed some heroics to stay alive until Fresno State failed on a two point conversion in the third overtime. The game also might have been over sooner, and less stressful, if the Aggies had put the ball in the end zone in the first overtime.

Despite what McGee might think, we no longer live in the days of the four horsemen and four yards and a cloud of dust. But is it possible that the rest of the nation has become too reliant on passing yards.

Aaron Schatz and the NFL stats pros at Football Outsiders2 point to the importance of net yards per pass play (including sacks). Some college teams consistently put up pass efficiency numbers that even the 2006 Colts didn't amass. Is the relationship yards per pass and offensive efficiency or, more important, winning the same as it is in the NFL?

My methods are simple and preliminary, based on data from all games including DI-A teams for the first five weeks of the 2007 college football season. But the results are worth noting.

I first ran simple correlations between same basic offensive statistics in a game and the Win/Loss outcome. Yards per pass play were highly correlated with success, with a pearsons r of .48. But total passing yards (TPY) was not significantly correlated with victory. More pronounced was the relationship between rushing and winning. Both total rushing yards (TRY) and yards per rush (YPR) had even higher correlations than YPP (yards per pass play), both exceeding .5. In other words, the initial analysis suggests that successfully running the ball is more important in winning football games than throwing the ball.

In fact, in turns out that achieving a higher YPP is, in large part, a product of not throwing incomplete passes. YPP and a teams completion percentage are highly correlated, but completion percentage is not strongly correlated with victory. It appears that passing can help a team win in two ways--producing first downs by consistent completions, leading to good field position or, perhaps more significantly, producing the occasional 90 yard bomb.

We also need to view TPY in context. Often teams will rack up meaningless yards in blowouts and in desperate efforts to come back from deficit in the last minutes. This is consistent with the result that TPY is positively correlated with number of points scored, even by the opposition. TPY is also generated by throwing more passes. Passes are also about twice as likely as rushes (4% of passes and 2% of rushes) to result in a turnover.

Successfully rushing the ball (TRY, YPR) and completing passes (comp, YPP) have the advantage of not only producing points (r=.50, .52, .35, and .58, respectively), but of preventing opponents from scoring (r=-.31, -.28, -.15, -.19, respectively). Not surprisingly, rushing is more successful at preventing opponents from scoring, because it uses more clock. Yards on the ground and completing passes also generate first downs and keep the opposing team off the field.

But the relationship between YPP, YPR, and TRY are not correlated with the opponent's TPY, YPP, and YPR and is only weakly correlated with TRY. Instead, the rushing the ball appears to be better correlated with better field position, so that opponents need to generate more yards to score.

Running teams have another advantage--it appears that production through the running game is more consistent and, therefore, more reliable. I used a simple model to predict a team's rushing yards by generating rating from past performances and subtracting from it an estimation of their opponents defense, again from past performances. By week 5, this model was better at predicting a team's rushing yards than a similar model at predicting passing yards. It seems rather intuitive that a rushing attack will vary less from game to game.

Not surprisingly, running the ball influences a teams ability to throw the ball. For example, if a team rushes for more yards they also tend to have higher yards per completion. This weekend, when Miami (FL) threw a 97 yard touchdown pass against North Carolina on a play action in a losing effort, they profited in yards per completion from the threat of running the ball.

It might not be appropriate, then, to focus on getting the right mix of running and passing. Easterbrook provided a nice discussion of the values of the spread offense, and efforts therein to find the correct run to pass ratio.3 The proper ratio for each team will vary with its ability to throw or run the ball--perhaps A&M should keep the ball on the ground. In reality, the proper call on any play is the one that has the best chance of accomplishing the primary objective--a first down, touchdown, or just getting a lot of yards very quickly. But, to appease my curiosity, I decided to ask--is there, generally speaking, an optimum pass to run ratio?

The values on the y-axis are the number of pass plays per run play. On the x-axis is the point margin. Overall, throwing fewer passes and rushing the ball more tends to result in a more favorable point margin. No team won in the week presented (week 4) while running twice as many pass plays are run plays (earlier weeks, when Texas Tech was winning by 50+, there are a few high-pass-ratio outliers; Hawaii, the other prolific passer, won by 56 with a pass to run ratio just under 2). A line of best fit, though, shows an upturn in the number of pass plays for those teams winning by 10 or more.

What, then, do we learn? First, in college football it is important, with a few exceptions, to establish a run game. Running the ball keeps your defense off the field, it forces your opponents to start deeper in their territory (in part because you are less likely to turn the ball over), and it sets up the pass (and vice versa). Passing the ball allows the occasional quick-strike touchdown, especially if the running game has sucked in the safeties, and can also be effective, like the running game, of eating yards and keeping the defense off the field if you are able to complete a lot of passes. Despite McGee's claim that Fresno State could not stop the run, if the Aggie offense had occasionally stretched the field with a play action pass down field, the might not have gone into triple overtime.

Finally, a target rate of between 2 and 1.5 run plays per pass play appears optimum for most teams in most scenarios. Obviously, a team should sacrifice ratios if they are losing by a couple of scores in the fourth quarter, but a powerful running game will prevent a team from finding itself in this situation.


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