The explanation is stuck somewhere between Philip Rivers's brain and his mouth, instinct once again failing to find words. Rivers is standing in the middle of a grass practice field at Chargers headquarters, gesturing with a football gripped in his right hand. It is an autumn afternoon, breezy and clear in Southern California, 48 hours before Sunday's kickoff.
All of Rivers's teammates are gone, and he's 20 minutes deep into a description of what is required to throw an accurate pass in an NFL game. He has talked meticulously as he pantomimed his routine, from snap to grip to drop-back to setup. He has demonstrated his wacky shoulder-push delivery—the result, he says, of throwing regulation-sized footballs with tiny hands at age six while watching practices of the high school team his father coached in Athens, Ala.—and now he has reached the point at which he releases the ball.
So Rivers is asked: How does he know where the pass will go, and how does he ensure it goes there? And here is the pause. Rivers wiggles the ball in his right hand, fingers across the laces as if ready to throw. He purses his lips, because this isn't easy to articulate. "You always want to pick a target," he says. "Like the chin [of the receiver]. But on some routes I'm throwing at the back of the helmet. A lot of it is just a natural feel."
Rivers strides forward with his left leg, brings the ball up to his right ear and then pauses in midthrow. "There are times," he says, "when I'm seeing how I'm going to throw it as I'm moving my arm. There's a lot happening at the time. Exactly where you're going to put it is still being determined."
Even as it's leaving the fingertips? More head-shaking and silence. Finally: "I don't know," says Rivers. "Like I said, there's a lot going on."
The forward pass is, along with the pitch, the most significant game action in American sport. Made legal in the rules of football just after the turn of the last century (while historians continue to debate its origins, they all agree that the first completion was not from Notre Dame's Gus Dorias to Knute Rockne in 1913, as suggested in cinema, and that it was probably some seven years earlier), it is the centerpiece of the most popular sport in the country, the play that determines the direction and outcome of most games and makes the NFL quarterback the most important of all team athletes.
Pro football has evolved from a run-based to a pass-based game. In 1977, the last year before rules changes that limited contact by defensive backs and vastly expanded receivers' freedom, teams averaged 37.4 running plays and 25.0 passing plays while completing just 51.3% of their passes. In 2009 teams ran the ball just 27.5 plays per game and threw passes on 33.3 plays, while completing 60.9% of passes. The number of passes per game was up to 34.0 through the first eight weeks of the 2010 season. The change has been steady and distinct.
But the act of passing itself is far more resistant to quantification. It is just as much art as science, because its lab is a kinetic (and dangerous) environment. "Early in my career I spent a lot of time studying," says former NFL quarterback Trent Green. "Then [coach] Norv Turner explained to me, your main priority has to be finding a way to do your job even though you're going to get hit right after you do it. Making a throw accurately and repeatedly despite getting blown up, that's what separates great guys from good guys."
From 1992 to '95 Steve Mariucci was the Packers' quarterbacks coach under Mike Holmgren; their chief pupil at the time was Brett Favre. "I had spent a lot of time drilling quarterbacks on fundamentals," says Mariucci, now an analyst with the NFL Network. "Drop back five [steps], hitch and throw. So my first year, Mike tells me to chart how often we actually throw that way, right on rhythm. At the end of the year I came to him and said, 'Mike, it was only 24 percent.' And Mike says to me, 'That's pretty good. My last year at San Francisco it was only 19 percent.' The point is, that fundamental throw, like the pitcher throwing off the mound or a golfer hitting a nine-iron, it just doesn't happen all that often. There has to be a variety of ways of getting the ball to the target."
As Rivers said, there's a lot going on.