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Passer Rating and Points Allowed

Less than 48 hours from now, the 2011 NFL playoffs will begin and much of the media hype and speculation will revolve around the high-octane passing attacks of the Saints, Lions this week and the Packers and Patriots next week. Indeed, this has been a season that has revolved around the passing game. Drew Brees and Tom Brady both topped Dan Marino’s 1984 record for most passing yards in a season. Aaron Rodgers set the NFL’s single season QB Rating record and Matthew Stafford threw for 5,038 yards and a 97.2 passer rating. Not surprisingly, these 4 teams were the top 4 teams in the NFL in offensive points scored. How closely is passing success related to points scored? Consider this: of the top 10 scoring offenses, all but 2 (Carolina and Houston) threw for over 4,100 yards. Of the 10 worst scoring offenses, none threw for more than 3,800 yards, and 4 threw for under 3,000 yards.

In today’s NFL, it’s tough to be a top scoring offense without throwing the ball with a lot of success. Therefore, we’d expect teams who can stop the pass to allow the fewest points. Here is how it looks in graphical form:

As you can see, there’s definitely a correlation between the passer rating a defense allows and the points per game it gives up (note: this is defensive points per game allowed, it excludes kick/punt return TD’s and points scored against the offense). The R2 is .62. In other words, about 62% of the variance in points allowed is due to passer rating allowed.

Another way to look at it is to divide the passer rating by the PPG. This gives us a league average of 4.14 – for every 4.14 points of passer rating allowed, a defense will yield one point on defense per game. I call this PTP (Points to Passer Rating). Here’s PTP over the last 41 years:

What stands out here is the brief spike in the early 90’s. As I mentioned in my series on offensive efficiency, the NFL saw a (very) brief “dead ball” era of about 3 or 4 years where offenses slowed down a bit compared to their output in the late 1980’s. For 2011, the team with the best PTP was the Pittsburgh Steelers (5.23). The worst was the Oakland Raiders (3.33).

If you’re curious, here are Passer Rating and PPG allowed since 1970:

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