The single most important position, in possibly all team sports, is the quarterback. Since the early 70s, quarterback performance has been measured by a calculation called Passer Rating. The Passer Rating was commissioned by the NFL in 1971 to standardize performance and have the ability to compare quarterbacks over a single game, season, or career. A team of statisticians used all data from 1960 to 1970 to create this formula, which was approved by the NFL in 1973.
The formula takes five passing statistics into four parts. These are attempts, completions, passing yards, passing touchdowns, and interceptions. The four components are as follows:
c = (comp/att – 0.3) x 5
y = (yards/att – 3) x 0.25
t = (td/att) x 20
i = 2.375 – (int/att x 25)
Finally, bring it all together and the Passer Rating = ((c + y + t + i)/6) x 100
I have created an excel template to quickly calculate passer rating based on the five statistics. You can download it here.
This formula has two constraints. The four variables cannot be less than zero or greater than 2.375. So if any of the calculations yield a result outside those constraints, then the minimum of zero or maximum of 2.375 is used. A perfect passer rating is then 158.3. The creators of the Passer Rating scaled all 1960 – 1970 data between 0 and 2.375 with 1 being statistically average.
For decades, this was accepted as the measurement of quarterback performance. Is it perfect? No. It does not factor in fumbles, rushing, or sacks but, after all, it is called a “passer” rating. In 2011 ESPN released their own calculation called Total Quarterback Rating, QBR. For a detailed explanation of the QBR, please click here. The CliffsNotes version tells us that the QBR is a weighted calculation that incorporates game context and how those plays transfer to wins. The rating ranges from 0 to 100. Sounds great, show me the algorithm! Ah…that’s where ESPN says hold on, this is proprietary. The QBR formula is not public.
So let’s see how these two rating systems stack up against each other. I pulled “qualified” regular season data only for each rating from ESPN.com for 2008 to 2013. You can explore the dashboard below. Note, ESPN states qualified data for passer rating means a player must have at least 14 attempts per team’s games played. There was no qualified definition for QBR data.
Select the statistic. This applies to Player Ranking table, the overall average, and the Distribution box and whisker plot. Year filter allows to view the Player Ranking for each single season.
Tableau 8.1 now has a one-click Box and Whisker Plot in the Show Me feature. This is a great function to analyze distributions. It is simple to read. In this case, QBs in the grey box are considered average, with the median being the value where the light grey and dark gray areas meet. QBs that fall above box and below the upper whisker are above average. Finally, QBs outside the whiskers are either exceptional or terrible, depending on the upper or lower whisker.
Looking at 2013, Nick Foles had the highest passer rating but Josh McCown had the highest QBR. But I think most will agree that Peyton Manning was the best quarterback this year. He’s number 2 in both statistics. And if you’re building a fantasy football team, you’d probably take 10-15 other quarterbacks before drafting Foles or McCown. My Washington Redskins had a dismal 2013 season. But 2012 was a great year. Robert Griffin III was 3rd in Passer Rating but 5th in QBR. He had an amazing regular season by any standards, incredible for a rookie. Let’s not talk about what happened in the post season. In general, a QB does not vary greatly between the two metrics. Upper tier players will have upper tier Passer Ratings and QBR scores and so on for mid and lower tier.
Since ESPN launched the QBR, they only use this metric in their broadcast. ESPN has it’s upsides and downsides. I find them only reporting a non-public metric they created on television to fall under the downside. Obliviously they do have Passer Rating on their website, where I got the data. Call me a traditionalist, but I prefer Passer Rating, mostly because I can calculated myself. How about you?