Stat Sheet Misconceptions: Passer Rating

| March 25, 2011

Before we move on to statistics for other positions, I think it’s necessary to examine my least favorite for quarterbacks, the Passer Rating. This number combines all of the basic statistics that are used to measure a quarterback’s passing performance into a single final figure, designed to be the ultimate evaluation for comparison’s sake. As you can see here, the Passer Rating is not the easiest number to make sense of.

According to NFL.com, “in rare cases” a quarterback will have a rating over 100. In 2010 alone, Tom Brady, Philip Rivers, Aaron Rodgers and Michael Vick all accomplished this feat and ended with ratings of over 100 for the season. Vince Young was also close to this “elite” level, finishing 5th on the list with a rating of 98.64, but I doubt many teams will be fighting to bring him aboard next season.

Here we will try to make their complex formula a little easier to handle, and then we’ll take a look at the flaws of the individual parts of the formula, the flaws of the formula itself, and why we can’t use passer rating to compare eras.
 

What Goes Into It

When websites attempt to explain passer rating, they’ll often have a step by step process that isn’t very easy to follow. However, if you’re willing to do some algebra and make some assumptions, the formula is simpler and looks like this:

The 42 quarterbacks with the most attempts in 2010 fit the assumptions, and, in general, we don’t need to worry about them when we’re looking at a large number of attempts. However, in the interest of completeness, the assumptions are: completion percentage is between 30% and 77.5%, yards per attempt are between 3 and 12.5 yards, touchdowns are thrown on less than 11.875% of throws, and interceptions are thrown on less than 9.5% of throws. If a number is above a maximum or below a minimum, than you assume it’s the maximum or minimum value and it still works out.
 

The Problem With What Goes Into It

We’ve already seen that completion percentage is imperfect, and while interceptions per attempt are better than just plain interceptions, many of the same problems we discussed remain. Yards and touchdowns, in my opinion, aren’t as bad, but are both still largely dependent on situation and supporting cast. Putting them all together in a formula doesn’t make them any less flawed, so the Passer Rating incorporates all of the problems mentioned in the past two articles plus some.
 

What’s Worth More?

The values that were used to determine the passer rating were chosen based on league averages from years ago, but even then, they didn’t make sense. Here is an example of why:
 

Quarterback A throws three straight passes, completing them each for three yards. Plugging three completions, nine yards, three attempts, zero touchdowns, and zero interceptions into the equation above, and you get a quarterback rating of 97.92, which is a very good rating.

Quarterback B throws three straight passes, the first two land incomplete, and the third is caught for a 30 yard gain. Putting those numbers into the equation, you get a quarterback rating of 71.53. In the first situation, the offense is now facing fourth down, where in the second the ball just went 30 yards down field.

 

The first quarterback has a rating of an all pro, while the second has the rating of someone fighting for their job.
 
The equation is basically saying that a completion is worth as much as 20 yards, a touchdown is worth as much as 80 yards, and an interception is worth -100 yards. It makes sense that touchdowns are worth more than yards, and interceptions are negative, but, as the example illustrates, completions are very much overvalued because in reality, they only help if they gain yards.
 
The relative values of touchdowns and interceptions don’t make sense either. You already know that I believe the interception is overvalued as an indicator for QBs. As for touchdowns, in a game, it doesn’t matter if a quarterback were to run for one or pass for one, yet there would be a significant difference in their passer rating. I would argue a touchdown is overvalued as well.
 

Historic Comparison

Because of an increased number of games played in the regular season, rules opening up the passing game, and offenses simply opting to pass more often , the all-time quarterback leader boards are slowly being taken over by more recent players. This is more true for Passer Rating than any other statistic.
 
A look at the all time leaders shows 25 of the top 30 QB’s by Passer Rating to be players who are either still playing or who ended their carriers in the past decade. Over the years, completion percentage, yards per attempt and touchdowns have all risen while interceptions have dropped; evidence that the environment today’s QBs are playing in is significantly different than that of years past. With other statistics, you can account for era to make a more fair comparison between quarterbacks who didn’t play at the same time, but for Passer Rating this doesn’t make sense.
 
Chad Pennington is currently ranked as the 12th best quarterback of all time in terms of Passer Rating while Hall of Famer Joe Namath ranks 182nd. Clearly we have a problem.
 

Closing Thoughts

While we will never get rid of completion percentage or interceptions, the passer rating is something I sincerely hope is eliminated from stat books someday. The difference being that completions, attempts and interceptions are all things that we count, and it’s just the way the numbers have been interpreted that has become flawed.
 
The purpose of Passer Rating is to provide one number to use for comparing relative passing success among quarterbacks, but there are better ways to do this. Most football statistics websites have developed a version of their own by re-working the current formula. We think the PFF pass grade for quarterbacks is the best tool to use when evaluating and comparing passing performances. Whatever way you look at it though, the NFL’s Passer Rating is out of date and is no longer needed.
 

  • tim tellean

    I agree. I’ve always found catch-all made up stats like these as problematic. I think this type of stat is great for the sports writers and ESPN broadcasters, so they can speak “intelligently” to the masses.

  • PaulK

    What I get out of your “Quarterback A” rating is the importance of down and distance in evaluating passes. On first and 10, a 3 yard gain is a defensive victory. On second and 7, the quarterback is at a disadvantage and should be gambling on a lower percentage pass to try to get at least 5 yards. On third and 4, a three yard gain is actually a pretty fair try at picking up a first down. His receiver couldn’t quite stretch out. The same play, different ratings.

    As for Quarterback B, he should get demerits for first and second down flubs, the first down flub is worse, because he put the offense in a big hole. On third down I give Quarterback B major credit for a first down which is what really counts for the offense, and only slight extra credit for ripping off the extra 20 yards.

    • Nathan Jahnke

      Good point that part of that is due to down and distance when I really just wanted to illustrate how completion percentage is way over valued. It’s hard to come up with an example that doesn’t involve first downs, since there are the min/max for completion % and yards/attempt. You’re still giving more credit to Quarterback B though, and he has a significantly worse rating. I agree it should be more about getting first downs though, and that is not factored in at all in the rating, where a good number of sites including ours factors that into our/their own QB ratings.

  • jakuvious

    I think the only real problem with passer rating is people thinking it signifies more than it does. Obviously, there is no way of measuring QBs accurately, and there never will be. The only way to accurately compare QBs is to watch them yourselves and form an opinion. All in all, as long as it’s taken with a grain of salt however, I think QB rating has actually come under a bit too much scrutiny by some circles. Obviously the mass media probably overuses it, but I think some criticism more recently has become a bit too harsh, regarding the statistic, simply because there isn’t really anything better, yet. I think the problem with QB rating isn’t so much the number it creates, but the fact that you can’t really form an accurate assessment of a QB from the statistics that QB rating draws from. I mean, take the Vince Young example. 60% completion, 8.0 ypa, and a 10:3 TD/INT ratio sounds like, at the very least, a very efficient season. The problem, really, is statistics in general, more than QB rating.

    • Nathan Jahnke

      I would agree with you that there will never be a fully accurate way to measure a quarterback(or any player in any sport), but there are better ways of measuring it than others. I would definitely say that measures like our PFF rating for passing is better than QB rating. If that’s way too different for the mass media at this time, then take something like http://www.pro-football-reference.com and their ANY/A. It is similar to the passer rating, but greatly improves on it. It takes out completion percentage which doesn’t need to be there, gives different numbers for the values of touchdowns and interceptions and has reasons behind them, includes sack numbers(and a metric that doesn’t include sacks if you don’t want), and doesn’t have the random number that you multiply things by or have the random constant. The flaws of it are similar to most stats in that they don’t account for situation and treat all yards and passes equal, but it’s still a step in the right direction compared to the passer rating.

  • baronzbimg

    Hi guys,

    as you mas know I’m a die hard fan of this site since 2008, it is the best football analysis site in the world when it comes to evaluating players, and it already was before last offseason’s makeover, yet I strongly disagree with your analysis.

    There’s no doubt statistics don’t tell the whole story of a player’s level on the field, and passer rating for a quarterback is one of them, yet disregarding “passer rating” as “out of date and no longer needed” is just wrong.
    Passer rating is flawed, it doesn’t take into account a lot of important quarterback plays like sacks and runs for instance, but its biggest flaw is that it has virtual limits. A quarterback gets a perfect passer rating when he completes 77.5% of his passes, throws a touchdown on at least 11.875% of his attempts, gets at least 12.5 yards per pass attempted, and of course doesn’t throw an interception.
    If he completes 90% of his passes with 14 yards per attempt and 4 touchdowns on 20 attempts without an interception, he gets the same 158,3 perfect rating when it should be more than 200. If you remove the artificial limits, a quarterback who doesn’t record a “perfect game” can in fact score better than 158.3.

    Yet as flawed as it is, passer rating is one of the most amazing stat in football because it relates to the only thing that should matter: winning.

    Teams that win the passer rating battle win 80% of the time. Passer rating differential (Offensive Passer Rating minus opposite team’s passer rating) is an amazing indicator of the quality of a team.
    Last year the Packers led the league in Passer rating differential. In 2009 the Saints led the league in Passer rating differential. Passing efficiency and pass defense are the most important qualities a team must have to succeed, it has an extremely high correlation to victory throughout history.
    .
    Bart Starr is the only quarterback to have won 5 NFL championships and he still holds today the best playoffs passer rating in NFL history (104.8 when the league average was below 80), better than Montana, Brady, Manning, Marino etc … He is a career 9-1 in the postseason, best career percentage ever. He’s the MVP of the two first Superbowls and the most underrated player in football history.

    Joe Montana holds the second best playoff passer rating in NFL history and he has won 4 Superbowls. You see a link here?

    More often than not the NFL glorifies volume numbers (passing yardage) over efficiency numbers (Yards per attempt, passer rating) whereas volume numbers tend to have no impact on the outcome of a football game. Besides the amazing play by play analysis you have here, passer rating should be the primary statistic to look at when judging a quarterback’s level of play.

    • CowboyJim

      Packer fans like me love coldhardfootballfacts.com! I used to hate passer rating, until I read all the info you mentioned at the aforementioned site. I think I hated it because I had Old Yeller fever, though. I would just like to point out that Aaron Rodgers now technically holds the mark for best career playoff passer rating. He’s got most of his career ahead of him though. Until then though I’m happy to let Bart Starr hold the reins.

      I also would like to say how much I appreciate what profootballfocus gives us and I love how there is such great analysis on football out there. I noticed that one of the writers that works here also works for coldhardfootballfacts. Maybe these two sites should pool together with the likes of pro-football-reference.com to make a “quality sites” list for the average football fan.