Nylon Calculus: Projecting rookie passers

Earlier this year, I introduced passer rating as a way to quantify passing ability. With it, we can understand the passing growth of a typical NBA player and forecast the ceiling of a budding star. But what if we peeled the onion even deeper and projected passers before they ever played an NBA game? Can we use college data to predict what a first-year playmaker will look like?

Thanks to Sports-Reference, passer rating is calculable for all NCAA players since 2010. Among the 106 rookies since then who were 22 or under, Ben Simmons authored the biggest jump between college and the pros (minimum 1,000 minutes played). But he was two years removed from LSU after redshirting the 2017 NBA season, so let’s disqualify that. #DistrustTheProcess.

Among “true” rookies, the biggest improvement belonged to Devin Booker, who posted a respectable 4.8 passer rating as a rookie after a Mr. Magoo-like 1.8 mark at Kentucky. (Passer rating essentially falls on a 1-10 scale.) Since Booker had far more room to grow than most, it’s not entirely apples-to-apples to compare his development with better passers. John Wall, for instance, improved nearly 2 points in rating as a rookie, to a healthy 7.1 mark, well above the average point guard that year. Accounting for difficulty, Wall’s growth seems just as formidable as Booker’s. Also, both played at Kentucky, which is worth noting since six of the 12 most improved passers were Wildcats. Something’s in the water down there.

In general, most rookies coming straight from college post a comparable rating to their final NCAA year, making collegiate passing fairly predictive of rookie-year passing. Since 2010, 78 percent of all 1,000-minute rookies have landed within a point of their college passer rating. Here’s what the distribution looks like, comparing changes from the final year of school to the first year in the league:

Opposing forces are at work here: Age and experience expand a rookie’s skills, but stiffer NBA competition and smaller roles reign in those gains. Rookie passers face a learning curve that is analogous to an NFL quarterback: coverages are more complicated, passing windows shrink faster and the game is more spread out. Free throw attempts are predictive of NBA passer rating, which suggests that the physically dominant maintain their passing angles as the difficulty ramps up.

Since 2010, 15 college players posted a rating of 7 or better in their final year of school. But only the barbate wizardry of Greivis Vasquez ever reached a rating of 9 in the NBA. That’s a small sample, but it underscores how much less room there is to grow when starting from those heights. Vasquez was also ahead of most on the aging curve because he entered the league at 24; passers generally peak in their early 30s, and some of the best distributors from recent classes haven’t fully ripened yet.

Case studies are fine and dandy, but what about something meatier? To forecast rookie passing, I whipped up a basic model that uses a player’s prior passing data (and free throw attempts) to predict his rookie passer rating. The model was fairly accurate, with 90 percent of players within 1.5 points of their actual rating. Here are the projected results for the the 2019 rookie class:

Claiming Luka Doncic is the best passing rookie this year is like declaring that the earth is round. Doncic’s stats are from the EuroLeague, a stronger environment than the NCAA, so some mental curving might be in order. Even so, the Slovenian adolescent (he’s only 19) posted one of the best pre-NBA passer ratings of the last decade while ceding years to most of the competition. The only other recent prospect on his level — and perhaps beyond — was Lonzo Ball, a hookup artist so gifted that his nickname should be Tinder. Ball dropped an 8.5 rating in his one year at UCLA before nearly replicating the mark as a rookie last year.

The other viral passer of this year’s class, Trae Young, shouldered a Westbrookian load in college but with marginal passing efficiency. He projects as an average passer for a point guard, which is ahead of many rookies, but his playmaking numbers might be volatile given that his on-ball load will likely drop by at least 25 percent. A less heralded lottery pick, Shai Gilgeous-Alexander, looks to rival him as a rookie distributor, particularly if he receives that Kentucky boost. And among the marquee big men, Wendell Carter Jr. projects as an above-average big man passer right out of the gate.

Ben Taylor is the author of Thinking Basketball and the Backpicks GOAT, an in-depth examination of the 40 best careers in NBA history. You can find passer ratings for historical players on his website.