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Cold, Hard Football Facts for May 10, 2005
How do you measure the consistency of a quarterback’s performance?
Without getting too involved, standard deviation essentially measures the distance a quantity is likely to lie from its average value. (You can find the formula for standard deviation and a good description of it here. We simply used an online calculator.) The smaller the standard deviation, the more consistent the set of variables. In our case, the variables we used were quarterback passer ratings.
Here’s what we did. We used our online calculator and entered the game-to-game passer ratings in 2004 of every quarterback in the NFL who started 12 or more games. We limited ourselves to only those quarterbacks who played at least 12 games because we felt this gave us a fair set of variables with which we could accurately measure a quarterback’s consistency from game to game over the course of a season and, more importantly, compare them to others. It's just not scientifcally reasonable, in this formula, to compare a quarterback who's played just eight games with a quarterback who's played 18.
We weren’t surprised to find New England’s Tom Brady near the top of the list. Consistency is a hallmark of his career in the NFL.
But we were surprised to find Marc Bulger of St. Louis standing unchallenged as the most consistent quarterback in football in 2004. In fact, it was even close.
In Bulger's worst game, at Buffalo, he posted a passer rating of 65.7. In his best game, home against the N.Y. Jets, he posted a passer rating of 116.4. In 16 games, that represented a pretty narrow range of passer ratings. In other words, you knew what you were going to get when Bulger stepped on the field last year. He was rarely spectacular, but he was almost always pretty darn good. That's a good guy to have running your team.
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Here, then, is our listing of NFL quarterbacks -- from most consistent to least consistent -- as measured by the standard deviation of their game-to-game passer ratings in 2004. Remember, the smaller the standard deviation the more consistent the player's performances.
Player, team (games) 2004 passer rating Standard deviation of passer rating
Marc Bulger, St. Louis (16) 93.7 12.9
Tom Brady, NE (19) 92.6 20.9
Aaron Brooks, NO (16) 79.5 20.9
David Carr, Houston (16) 83.5 23.4
Peyton Manning, Indy (18) 121.1 24.9
Josh McCown, Arizona (14) 74.1 25.0
Carson Palmer, Cinci (13) 77.3 25.9
Daunte Culpepper, Minn. (18) 110.9 26.2
Vinny Testaverde, Dallas (16) 76.4 26.2
Kyle Boller, Baltimore (16) 70.9 26.5
Joey Harrington, Detroit (16) 77.5 26.9
Jake Delhomme, Carolina (16) 87.3 27.5
Byron Leftwich, Jacksonville (14) 82.2 28.1
Jake Plummer, Denver (17) 84.5 28.9
Trent Green, Kansas City (16) 95.2 29.2
Drew Bledsoe, Buffalo (16) 76.6 29.2
Kerry Collins, Oakland (14) 74.8 29.4
Donovan McNabb, Philly (18) 104.7 30.8
Chad Pennington, NYJ (15) 91.0 31.4
Matt Hasselbeck, Seattle (15) 83.1 31.7
Ben Roethlisberger, Pitt. (16) 98.1 31.8
Brett Favre, Green Bay (17) 92.4 32.7
Drew Brees, San Diego (16) 104.8 34.3
Michael Vick, Atlanta (17) 78.1 36.0
Obviously, looking at a quarterback's overall passer rating helps us make a further critique of a player's consistency. We were able to group many of these players into one of four categories:
THE CONSISTENTLY BAD
If a player has a low passer rating and low standard deviation, that simply tells us that he was consistently bad. Arizona's McCown is a prime example of this. Yes, only five quarterbacks were more consistent last year, including several Pro Bowlers. But with a 74.1passer rating, the second lowest of any quarterback on our list, saying that McCown is consistent is not saying much.
THE INCONSISTENTLY BAD
Three quarterbacks stand as out inconsistenly bad. That is, their low passer ratings show that they were bad more often than not, but their high standard deviation indicates that they showed glimpses of brilliance during the season. Besides Vick, who we already discussed, this list includes Collins and Bledsoe. Both were among nine quarterbacks with sub-80 passer ratings in 2004. But both recorded standard deviations approaching 30. Collins's poor season was interrupted by a 371-yard, 5 TD performance against Tennessee. Bledsoe broke rank with a 277-yard, 4 TD performance against Miami in which he completed 19 of 30 passes. These players register high on the fan infuriation meter.
THE INCONSISTENTLY GOOD
Three quarterbacks also stand out as inconsistently good. These players posted high passer ratings and high standard deviations. Brees, Roethlisberger and McNabb each posted passer ratings that stood among the very best in football. But their high standard deviation indicates that their frequent great games were often interrupted by rotting hambones. Brees tanked against the Jets and Denver, with a pair of sub-50 passer ratings. Roethlisberger impressed for much of his rookie season, but found a nemesis in New York. He posted meager passer ratings of 33.6 and 57.8 -- his two lowest of the season -- in two games against the Jets. McNabb spit the bit against Pittsburgh, passing for just 109 yards and posting a passer rating of 55.7.
THE CONSISTENTLY GOOD
Conversely, a player with a high passer rating and low standard deviation was consistently good. Again, three players stand out: Bulger, of course, along with Brady and Manning. Seven quarterbacks posted higher passer ratings than Brady, but only Bulger was more consistent in his performances. And, of course, Brady got better as the season wore on (five of his 10 100-plus passer ratings were posted in his final seven games). Manning, meanwhile, was spectacular. Not only did his passer rating in 2004 put all others to shame, he was also the fifth most consistent quarterback in football. His season looks even better when you dismiss his token appearance in a meaningless regular-season finale against Denver. Manning threw just two passes and registered a 56.3 rating in that contest. We recalculated his standard deviation without this game and found that it dropped to a mere 21.2. Subtracting this Denver variable from the equation means Manning would have moved one spot up the list, leap-frogging Carr.
GO RAMS!!
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