The folly of the 'perfect' passer rating
Cold, Hard Football Facts for Dec 05, 2010
By Luis DeLoureiro
Cold, Hard Football Facts perfectionist of pigskin
Tom Brady put on a clinic in his last game, New England's 45-24 win at Detroit on Thanksgiving. But was he really perfect, as his statistically "perfect" passer rating of 158.3 would suggest?
The short answer is no. In fact, his effort wasn't even the best passing performance of Week 12.
Brady may be having his best season, even when compared to 2007. And he did produce one of the best games of his career against the Lions:
21 of 27 (77.8%) for 341 yards, 12.63 YPA, 4 TD, 0 INT, 158.3 rating
It was the only "perfect" passer rating by any player this year, at least given the indicator's archaic method of calculation. And so, given those lofty numbers, we're not going to hold it against him that he's started to pitch women's clothing accessories.
The trouble with statistical tribbles
As you know, we like passer rating because it has a high correlation to success. However, the NFL's passer rating certainly has its share of issues. And at the top of the list may be its arbitrary definition of "perfect."
It didn't matter much when the indicator was created in the early 1970s and "perfect" passer ratings were spotted about as often as a CHFF reader at the gym. But it's a growing issue these days, as passer ratings are more inflated than ever.
Let's take a step back and look at the indicator. The NFL's passer rating is a combination of four factors:
- Completion percentage
- Touchdown percentage
- Interception percentage
- Yards per attempt (YPA)
The problem is that the rating has arbitrary boundaries for each factor. A player is considered to have had a perfect game if he:
- Completes 77.5 percent of his passes
- Completes 11.875 percent of his passes for touchdowns
- Throws zero interceptions
- Averages 12.5 yards per attempt
In other words, if a player throws 16 passes and two of them are for touchdowns (12.5%), any touchdown pass he throws for the rest of the game will not improve his rating.
It creates very odd situations. Consider the following:
One – If Brady had thrown one more pass – and it had fallen incomplete – his perfect game would have been gone. His rating would have dropped to 154.9.
Two – If Brady had completed three more passes – all for 10 yard touchdowns! – his numbers would be 24 of 30 for 371 yards and six touchdowns. And his passer rating would drop, too, to 157.7!
Three – We're pretty sure the NFL's passer rating formula is the only place where you'll find a scale of 0 to 158.3 (actually, 158.3333333 to infinity) to measure a player's performance. It's like Kelvin for those who grew up taking temperatures with Fahrenheit.
As stated above, Brady has generated the only "perfect" rating of the season so far. But for the sake of this conversation, let's recalculate the passer ratings for every game this season – with the aforementioned boundaries removed.
For example, below is a table showing Brady's rating from the Detroit game. It's broken down by each individual category of passer rating. It compares his rating in the current system vs. an adjusted calculation with the artificial boundaries removed.
|Category||Value||Traditional Rating||Adj. Rating|
As you can see, removing the limits of the traditional system would give him an adjusted rating of 168.9.
David Garrard: tops in 2010
By removing these artificial caps on passer rating, we find that Brady's effort against Detroit was only the third-best performance of the season.
Jacksonville's David Garrard posted the season's most highly rated performance (184.6) in Week 8 at Dallas, a 35-17 Jaguars victory. Jay Cutler is No. 2 on the list, for his 170.1-rating effort in a 31-26 win over the Eagles in Week 12. So it turns out Brady didn't even have the best game of the week.
Top Passing Performance of 2010 (uncapped passer rating)
|Peyton Manning||NY Giants||2||145.5|
We're going through the historic numbers now. But we believe Brady does in fact boast the highest uncapped passer rating, at the very least, in recent history.
He completed 21 of 25 for 354 yards, 6 TD and 0 INT in New England's 49-28 win at Miami in 2007. That works out to a 211.1 uncapped passer rating.
Drew Brees nearly matched the mark last year against – ironically enough – the Patriots. He completed 18 of 23 for 371 yards, 5 TD and 0 INT in a 38-17 Saints win in New Orleans. As we reported at the time last year, it gave Brees an incredible 207.0 passer rating.
We still like passer rating. As you see, almost all of these big efforts came in victories. So our main problem with passer rating is that it's not, well, perfect.
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