I don’t think Mark Twain was talking about the NFL when we uttered those famous words, but he may as well have been.
NFL-land is populated by all sorts of numbers. Some of them interesting, some of them obvious, and some of them largely irrelevant. All of them, however, often used to promote one agenda or another.
The one that really gets me? It’s the abuse of the sack stat.
The Sack Stat
How do you know a defensive lineman had a good year? Look at his sack numbers. How do you know an offensive lineman had a good year? Look at how many sack he gave up. It’s the simplest way to do things–after all, it’s near impossible to break down every game without having an entire team dedicated to doing so.
The only problem is those sack numbers are extremely limited.
The sack stat tells you that Jared Allen had 22; more than any other player in the league. But that number doesn’t tell you who they came against, or how many opportunities he had to rush the passer. The sack number doesn’t account for the quarterback who kept pressure from turning into sacks, and it doesn’t tell you at what point of a game they came.
See how limited it is?
Take a look at a player like Eugene Monroe, for example. He gave up nine sacks last year. Sticking in the AFC South, how about we compare that to, say, Michael Roos. The Titans' left tackle gave up just one sack the entire year.
A slam dunk case of one tackle being better in pass protection than the other, right? Well, how about we look at some more numbers that compare the two.
Player Team Pass Block Snaps Sacks Hits Hurries Total Pressure PBE Time in Pocket
Eugene Monroe JAX 444 9 4 12 25 95.3 2.8
Michael Roos TEN 619 1 9 25 35 95.7 2.4
Suddenly things aren’t quite so clear-cut. In fact, while Roos walks out with a slightly better Pass Blocking Efficiency rating (a statistical way of measuring a player's pass protection), it’s nowhere near what the sack numbers would suggest. What’s more, you can see a column at the end entitled ‘Time in Pocket’. This is the time from when the ball is snapped to when the quarterback has finished passing, taken a sack, or scrambled past the line of scrimmage. Roos, on average, had to pass protect for four-tenths of a second less than Monroe on every play.
This might not seem like a big deal until you consider that over the course of the season that means Monroe spent an extra 242.4 seconds in pass protection. Again, not a number that seems like a lot, but realizing the average pass play takes around 2.8 seconds, Monroe in essence had to face 86 extra passing situations because his quarterback held the ball longer.
It’s not an exact science, but you get my point: statistics in the NFL are not an exact science.
Defining the Lines with Sack Sums
Still, when people fire away talk of the worst offensive lines, they look at those sack numbers. It’s why recently I’ve had someone explain to me that the Giants' offensive line was better than the Cowboys' offensive line because Tony Romo took more sacks than Eli Manning.
For a start, this doesn’t include sacks that are on the quarterback for holding the ball too long. We define ‘too long' as being anything over four seconds, and in this regard Romo leads Manning 3-to-1. It also doesn’t account for sacks pegged to skill position players who have stayed in to help, where the Giants only gave up one sack compared to two for the Cowboys.
But more importantly it doesn’t account for the quarterback's ability to get rid of the ball and avoid sacks. If you want to look at this in number form, we have a nice little figure that shows the amount of pressure each quarterback faces and the percentage of that which ends up in a sack. The Giants' QB is down at 11.5% (lowest in the league), while the Cowboys' passer is up at 20.6% (10th-highest in the NFL).
You see that’s the beauty of stats. You dig a little deeper and you find something that can expose the limitations of another. A perfectly executed cross examination, if you will.
The Impact of Pressure
See here’s the thing: sacks aren’t the be-all and end-all. If you think they are, you’re either confused, foolish, or someone who just doesn't get football.
The idea of pass rushing is to get to the quarterback and influence him. Now, a sack is the ultimate form of influence as it results in a guaranteed negative play, but you better believe that hurrying a quarterback makes life a lot harder for a passer. For some numbers to back that up, have a look at the combined stats for the 35 quarterbacks who dropped back from center more than 200 times last year:
Situation Att. Comp. Comp % Yards Y/A TD INT TD:INT
Without Pressure 11152 7324 65.70% 86440 7.75 541 273 1.98
With Pressure 3895 1791 46.00% 23306 5.98 133 147 0.90
It doesn’t take a genius to figure out that pressure increases your chances of throwing picks while hindering your ability to complete passes and significantly reducing your yards-per-attempt average. It’s kind of the difference between having Tom Brady as your quarterback and Tim Tebow throwing the ball; only you don’t get any of the benefit of Tebow’s athleticism.
And people say pressure doesn’t really impact your quarterback.
It’s Just a Number
You know what the annoying thing is? If used correctly, the sack number is an important tool. It is often representative of the amount of pressure a player is getting, and as the ultimate play a pass rusher can make (the one guaranteeing a negative play for the offense), it is hugely important. But it’s a part of the puzzle, not the entire thing.
For pass rushers and pass protectors that means looking at all forms of pressure and then breaking down how quickly these pressures come. As analysts, that means looking at what times a pressure comes in a game and against whom it comes. We stand by our grading as being the best tool out there for identifying the best pass rushers and best pass protectors, after all it looks at how quickly a pressure comes, when it comes and how often it comes.
But even that, the most advanced measurement of play, shouldn't be treated as gospel.
So, whenever you look at any numbers regarding sacks, pass rushing, or pass protection don’t just switch off. Look into them, because often times the face value won’t tell you the whole story. It’s how the team at PFF uses them and, if you really want to understand what’s going on, take off the blinders and do the same.