It is no secret that I am not a big "stats guy". While I appreciate the efforts of organizations like Football Outsiders, I still feel that they are light years behind Baseball or even Basketball in terms of the quality and breadth of their advanced statistics. In fact, I am not sure Football will ever be able to catch up due to the very nature of the games themselves (SSS). That said, I do see meaning in some stats when they are well-interpreted.
My intent here is not to start a long, tedious debate about the relevance of numerical data to Football, but rather to illuminate two statistics that I believe can tell us something about the game: Yards per (pass) Attempt and Yards per Carry.
Before I jump in I just want to cite two people who have written about this before me. The first is SBN's own Ross Fulton over at Along the Olentangy, who teams up with Tyler T. (formerly Gahnki here) to write an excellent OSU blog. The second is Chris Brown at Smart Football, who is a genius.
The stats themselves
Yards Per Pass Attempt (or Yards Per Pass Play) is a measure of the yardage gained on passing plays divided by the number of passing plays, sacks included.
Yards Per Carry is a measure of the total yards gained by running the ball, divided by the number of running plays.
Both YPA and YPC should not favor consistent, steady players ("dink and dunk passers", RBs who consistently gain a few yards but seldom break a big run) nor should they favor big play machines (long ball throwers, home run hitting RBs). They should favor players who produce yardage.
These stats essentially aim to measure the yards gained per play when a team passes or runs the ball, respectively. Easy enough.
There are times when offenses do not seek to maximize their yards per play. Sometimes 1 yard or even a few inches will do the trick; 3rd or 4th and and short, on the goal line, etc. There are a million contingencies that dictate an offense need not seek maximum yardage.
I do not believe in YPC or YPA as purely individual statistics that correctly evaluate players. It takes a lot of effort to separate one player from his team in football. This could go on forever but it really isn't what I am driving at, so I'll just leave it at that for now. I view these as team stats.
Lastly, for reasons that will become clear, I do not believe that YPA or YPC measure how good a team is at running or passing the ball in absolute terms. I am much more interested in these stats relative to one another.
Many commentators and fans look to the number of running vs. passing plays an offense has called to see if they are "balanced". I do not believe in this.
Instead, I like to look at YPA vs. YPC.
The idea is simple; if you average 4 yards every time you run the ball, but 10 yards every time you drop back to pass, you are leaving yards on the table by running the ball.
Side note: The "Passing Premium"
With regard to these numbers, it is important to understand something many have dubbed the "Passing Premium". This premium is an emphasis that coaches put on gaining yards through the air versus on the ground. Basically, passing is riskier than running the ball; there are more opportunities for turnovers (both interceptions and an increased risk of fumbles after the catch), the average yardage floor is lower. Every time you drop back to pass, you increase your risk of turning the ball over or being put in a 3rd and long situation.
To counteract that increased risk, coaches want more reward when passing. This increased reward of about 1-3 yards per attempt is the passing premium: If a coach has to deal with the increased risks of passing the ball, he wants to get 1-3 yards per play more vs. running the ball.
Back to Balance
A balanced offense is one where the offense averages the same amount of yards per passing and rushing attempt, while factoring in the passing premium. This means a balanced offense averages 1-3 more yards per attempt than they do yards per carry.
Think about it, if you average a measly 2.94 yards every time you run the ball, and you average 7.3 yards every time you pass the ball, what would you do? You'd pass the damn ball. The 4.36 yards per play difference is much larger than even a conservative passing premium. You'd be leaving yards on the table every time you ran the ball.
Where did I get those oddly precise numbers? They were the Browns' actual YPP averages against Kansas City, a game where many criticized the coaching staff for passing too often and not "establishing the run". Based on the results, we should have actually passed the ball more.
The Nash Equilibrium and Adjusting
The problem with spamming one phase of the game play after play after play is that unless your offense is just miles better than the defense in that phase, the defense will adjust and the defense will take that phase away. You will see diminishing returns on your running game if you never threaten the pass.
Let's take the Wisconsin Badgers as an example. They are clearly good at running the ball: running is their identity, it is what they recruit for, they have a massive offensive line and three legit D-1 running backs.
When the Badgers come across a team of equal talent who can stop their running game, that team will have probably committed many of their defensive resources to do so: they'll walk an 8th or 9th man into the box, they'll substitute for run vs. pass, they'll scheme for the run, etc. Wisconsin will see it's YPC go down. Then what should they do? Pass the ball, even though they aren't as good at passing. Chris Brown says it best:
You pass of course. You run bootlegs, you fake it to him, and you throw the ball. But how odd you say. You have the best running back you've had in 15 years, and you wind up running less? The answer is simply that everyone else knows you have this stud RB, so they commit so much effort and defensive scheme and structure to push your expected yards per rushing play down to a manageable number, your passing opportunities increase, even if you have less talent there than years past.
Once Wisconsin completes a few PA passes, the defense must again respect the pass, adjust accordingly, and that re-opens the running game.
Though it is counter-intuitive, this means that sometimes you may see a dip in a player's or team's stats because they are good. They are so good, in fact, that defenses adjust to whatever it is away, knowing that they will be vulnerable elsewhere.
While the Browns are probably better at running the ball in absolute terms, we still need to keep defenses honest by being a balanced offense. This does not need to be reflected in the amount of rushing vs. passing attempts, but it does need to be reflected in the per play averages for us to be successful.