Tuesday, August 24, 2010

The Elusive Pass Rush Part I: The Sack Artist

Watching your team sack an opposing quarterback is among the most satisfying and exciting moments in football. It also is something the Seahawks have had a lot of trouble doing the past few seasons. If you tune into any local sports radio show, you will likely hear them talking about how the Seahawks need to generate a pass rush. Players such as Chris Clemons, Nick Reed, Aaron Curry and Dexter Davis are thrown out as hopeful sack artists despite none of them ever having more than 8 sacks in a season.

Ask the average football fan how many sacks a player needs to have in order to be considered a legitimate threat, the most common answer will be 10. Nobody would argue that 10 sacks is a good-to-great year for a pass rusher. Yet, I can only remember two Seahawks in the past eight seasons to reach that level (Patrick Kearney and Julian Peterson). Is it really that hard to get 10 sacks? That's only 0.6 sacks/game, or basically a sack every other game. I decided to do a little research to see just how hard it is to record 10 sacks or more in a single NFL season, and the results surprised me.

In baseball, hitting over .300 is generally considered a good year of hitting (OPS and other sabermetrics aside). How many hitters are having a good year in 2010? Twenty-three of 158 batters with enough at-bats to qualify (i.e., 15%) are hitting over .300 this year in baseball. By those percentages, finding a .300 hitter is a piece of cake compared to finding an NFL player with 10+ sacks.

Over the past eight seasons, an average of 15.38 players per season have had 10+ sacks. It's safe to say that sack leaders are always either defensive lineman or linebackers, and that there are seven of those on every team. With 32 NFL teams, that adds up to 224 players with 10+ sack potential. Amazingly, that means a scant 6.86% of starting NFL lineman and linebackers record 10 or more sacks in a season. Think about that for a second. Seven out of every 100 LB+DL. These guys certainly don't grow on trees.



In figure 1, you can see the total number of players in each of the last eight seasons that have recorded 10 or more sacks. It is worth noting the drastic drop-off across the league in the last few seasons after a rather steady increase from 2002 to 2006. It's unclear if rule changes, better lineman, or a reduced number of capable sack men are to blame. What is clear is that if you were a head coach in the NFL last season, you had less than a 6% chance of having a player reach the 10 sack mark.
Once a player gets to 10 sacks, there is not usually a whole lot separating him from the elite pass rushers. As you can see in figure 2, the average number of sacks recorded from the Top 5 sack masters in each season generally hovers around 14 sacks. That's the difference of 0.25 sacks more/game, compared to a player with 10 sacks. Other than DeMarcus Ware's 20 sack outlier, the league leader is often between 16-18 sacks. The absolute best sack artist in the league averages a little over 1 sack per game.

The Seahawks have had only two players reach the magical 10 sack level in the past eight seasons. Those 8 and 8.5 sack seasons from Chike Okeafor don't seem so pedestrian anymore, do they? In figure 3, you can see how the Hawks sack leader has performed.

It may be a coincidence, but the trend here correlates pretty closely to the one in figure 1. That is, as there were a growing number of players with 10+ sacks, the Seahawks sack leader had a growing total as well. Similarly, the Seahawks saw a massive decline in the last two seasons with their sack leader coming in at 5.5 (2008) and 5.0 (2009). In part two of this series, I will take a look at overall team sack numbers to see if we are seeing a general decline in sack numbers across the NFL, or just a diversification of who is getting those sacks.

What I walk away from this data now knowing is that 10 sacks is probably an unattainable goal for any Seahawk this season. The likelihood of finding a guy like that off another team's scrap heap (e.g., Chris Clemons), a late-round pick (e.g., Reed, Davis), or a player that recorded two sacks the year before (e.g., Curry) is almost nil. A reasonable goal for this season is to get someone back to the 8-sack level, something Chris Clemons has done before.

In part two, I will also explore the correlation between sacks and winning. Namely, does being a team that succeeds in sacking the quarterback make you significantly more likely to be a Super Bowl contender? Is it a prerequisite? We'll find out.

3 comments :

Mr Posh said...

This is a really interestig article and very insightful.

(1) I love stats
(2) I love sacks

Order not specific!

I would like to know though (I will investigate) that whilst the percentage of players with credible sack numbers (10+) has declined, has the overall number per team declined by the same percentage also from 2007 (this was the marker year when it dropped off??).

If not it would clearly indicate more of a spread between players who account for the total number of sacks per team.

Other reasons I would need to establish.

hawkblogger said...

Glad you like it Mr Posh! Good news. I've actually already got the team sack numbers, and will be publishing those today as Part II of this series.

Mr Posh said...

Yes, I like it very much :) Keep up the good work.

Quality re the team sack numbers - I await with baited breath! :)

I wonder how Mark Gastineau, Reggie White, Lawrence Taylor, Tez et al would have fared in today's game? Reggie White could have played any era though, IMHO.

Looking forward to today's post...my instinct says there will be a slight drop but nothign quite so severe.