According to the New York Times, the Jets coach "cares deeply" about passer rating, that much-maligned, simplistic, often misleading statistic dismissed by many as a curio. He uses it to evaluate his and opposing quarterbacks, and considers it one of the leading indicators of team success—even as it notoriously elides contributions from the other 21 players on the field.
"The amazing thing is at first, I was like, What is this?” Ryan said, referring to his understanding of passer rating. “It wasn’t that big a deal to me."
That was until Ryan realized the correlation between a higher passer rating and victory—fairly steady around 80 percent over recent seasons.
The correlation isn't a surprise. The passer rating formula takes into account completion percentage, yards per attempt, TD percentage, and INT percentage. If you win those battles, you're generally going to win the war. But while compressing four separate statistics into a single one makes for simple shorthand, it tells you less about a quarterback than if you consider each one individually. It's like assuming Adam Dunn and Brett Gardner are similar players because they have near identical OPS figures.
Passer rating ignores QB rushing yards, fumbles, and sacks. It disregards the ground game, even though it can have a huge impact on a QB's success, or lack thereof. It can't tell you anything about a quarterback's supporting cast, or the quality of the defense it was recorded against. The NFL's official formula explanation even notes that "statistics do not reflect leadership, play-calling, and other intangible factors," though in its defense, any statistic that attempts to measure intangibles should be immediately dismissed.
Passer rating has its defenders, perhaps increasing since ESPN's attempt to create Total QBR, which does try to take into account clutchness, an intangible. (Or at least there's significant debate on how to quantify it.) Speaking for passer rating is how remarkably consistent an indicator of success it's remained over time. Since 1940, 25 percent of NFL champions have led the league in passer rating, and 96 percent have been in the Top 10. But what does this actually tell us beyond "teams that are successful are successful at throwing the ball?"
It's tough to find a stat that's predictive. Giving significant weight to passer rating is akin to saying a quarterback is good because his quarterbacking stats are good. It isn't much more than a tautology.