The Overrated Sack

Every year I make it my mission in life to come up with new and creative ways to show the sack stat is the most abused one out there.

Sure, for some people it can be a reward for consistent play, but many others benefit from people caring too much about a small sample size, or, in some cases, players are punished because people don’t pay enough attention to what they actually do on the field.

Sample Size

Here’s what really gets me about the sack stat. You’re judging a player by what he does on a small percentage of his plays, and using that small percentage to assume a whole lot about the rest of his game. Now full disclaimer here, PFF doesn’t credit ‘half sacks'. No. we count a half sack as a full sack for an individual, so we’re a little bit kinder to pass rushers in this regard. But even so, have a look at the table below that represents how many plays on which a pass rusher records a sack.

Sacks by Total Defensive Snaps

[table id=766 /]

J.J. Watt had an incredible year. In fact we’d go as far to say it was a year for the ages, and it earned him our inaugural Dwight Stephenson Award for the best player in football. But it’s a shame he needed to lead the league in sacks to build his case, because his year was about so much more.

Indeed, the table shows Watt picked up a sack on just 2.35% of his total defensive snaps, and that number doesn’t include plays nullified by penalty where stats aren’t recorded. Fortunately, by leading the league he got the praise he was due, but what about a guy like Aldon Smith, who finished second in the voting for defensive player of the year. Not one of the better run defenders in the league, he essentially earned his votes on the back of his play on 2.1% of his defensive snaps.

Is that fair?

People will say he played better than Von Miller because his sack number was higher. Yet they discount that Miller had a higher sack percentage and 12 more tackles for a loss in run defense or in coverage than Smith.

Time to Sack

People also fail to realize that not all sacks are created equal. The average time to sack in the NFL is 3.8 seconds, although this owes something to 305 instances of a sack taking five seconds or more. In our grading system we reward sacks that come under three seconds (and without a QB being forced into the lap of a defender) with a heavier positive grade.

Indeed, we don’t really know of many passing plays that require the QB to hold onto the ball for more than four seconds. So, you’re either looking at the passer not getting rid of the ball quick enough, or the coverage unit doing such a good job that he can’t. Either way it’s a sack that isn’t entirely down to the pass rusher, though he gets all the credit.

Let’s look at the table to see what it shows us.

Time from Snap to Sack

[table id=767 /]

Now, I don’t mean to continually promote Von Miller, but do you not think him getting nine sacks in less than three seconds is slightly more impressive than those who picked up theirs after four seconds?

Nature of the Sacks

However, even taking sample size and the speed of a sack in to account doesn't make things crystal clear. You see, some sacks are earned and some are handed out. What about if a pass rusher actually had to beat a man to earn his sack? Sometimes a guy is left unblocked, sometimes the pressure from elsewhere pushes a quarterback into a player's lap, and sometimes he just chases down a quarterback in pursuit who should get rid of the ball.

Adjusted Sack Count

[table id=768 /]

Look at these numbers closely. All of a sudden that magical number Aldon Smith produced doesn’t look quite so healthy, while the total Von Miller managed looks a little inflated. Meanwhile, poor old Julius Peppers got just the one freebie. That doesn’t make him a better pass rusher, but it should help you understand the sack stat is one that shouldn’t earn a great deal of your trust.

The Alternatives

We understand the need to quantify things with numbers. We do it ourselves. On the PFF Premium package you can go back to 2008 and check out numbers that don’t worship the small sample size produced by looking at sack numbers alone. We’ve got hits and hurries, and what’s more we’ve got the all important context — pass rushing snaps. Going beyond this we have our grades that take into account how quickly pressure happens and if a player had to do anything to get it.

The information is there. You don’t need to be a slave to the sack stat anymore and can instead appreciate players for more than what they do on 2% of plays.

Follow Khaled on Twitter: @PFF_Khaled