WESTLAKE, Calif. – The drafting and recruitment of quarterbacks remains the most unpredictable variable amid two billion-dollar industries that rely disproportionately on the productivity of that position.

The most important position in all of sports still somehow remains the most difficult to evaluate, as attempting to quantify how a quarterback processes information, reads defenses and works through his progressions resonates simultaneously as one of the game’s most critical and difficult ventures. In the NFL and college football, there are millions poured annually into scouting, recruiting and attempting to decode football’s final frontier.

“The makeup of the quarterback is such a rare and unique collection of factors,” said longtime NFL executive Mike Tannenbaum, now a draft analyst for ESPN. “Processing is so important, and until [the quarterback is] under center and taking snaps, you really don’t know.”

For all that’s tangible in quarterback evaluation – arm strength, athleticism and speed – there’s so much that’s difficult to ascertain.

Why were Tom Brady and Russell Wilson passed over by every NFL franchise before becoming Super Bowl champions? Why will Jake Locker, Geno Smith and JaMarcus Russell long be remembered as busts? Why did Mitch Mustain turn from a five-star to an afterthought while Andrew Luck soared to the top pick in the NFL draft?

View photos Why is it so hard to identify quarterbacks who will excel at the highest levels of football? Because processing at the most important position in sports is a science that hasn't yet been mastered. (Yahoo Sports illustration) More

Much comes down to the intangible and unquantifiable – processing seamlessly amid chaos, adjusting to defenses pre-snap and the ability to react and think under pressure. There are some scientific attempts to quantify the brain, reaction and instinct, but for now it remains one of the sport’s great unknowns.

“Whoever figures out how to teach processing and can explain how they do that to everyone is going to be a rich man,” said Will Hewlett, a Texas-based private quarterback tutor. “It's harder to put your finger on than physical traits, skills, even leadership qualities.”

The unrefined process behind figuring out how well a quarterback processes information begins, in most cases, long before their senior year of high school. UCLA coach Chip Kelly has tried to crack the code of the quarterback’s mind as both a college and NFL head coach.

In recruiting, he said the best way to evaluate the mind of the quarterback comes from an unofficial visit early in the prospect’s career. There’s a chicken-egg dynamic that makes this a tricky tightrope, as Kelly wants to sit down with a quarterback recruit and go over offense on the board with him to get a sense of how he processes and thinks about the game.

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Ideally, that would happen on campus on an unofficial visit. But sometimes recruits won’t take the unofficial visits without having already received a scholarship offer.

“The [recruiting] process is going faster and faster with people offering freshman and sophomores, and I think they're just throwing offers out and hoping they hit on somebody,” Kelly said. “I think it has [made things harder]. And the kids feel like, ‘Well you don't like me because you haven't offered.’ Well, I don't know if I like you because I haven't met you yet.”

Stanford coach David Shaw, like many coaches, puts an importance on getting recruits to camp to evaluate their processing ability.

“I like to see when he goes from his primary to his secondary and third read,” Shaw said. “The timeframe for him to see it, diagnose it and get the ball out of his hands. That usually shows processing speed, to see it and get it out of his hands quickly.”

At camps, Shaw likens giving quarterback recruits new plays and concepts to the processing speed of a computer. “How quickly can you diagnosis it and make a decision?” Shaw said.

Everyone agrees that time with quarterbacks helps clear the fog of mystery in how well they process. Northwestern coach Pat Fitzgerald says his program takes concepts that teams use at the NFL Combine to evaluate high school quarterbacks.

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