Moneyball’s Draft Advice Has Outlived Its Usefulness

Of all the draft lessons MLB learned from Michael Lewis’s seminal book “Moneyball” — including that scouts should disregard how good a player looks in jeans — one of the most prominent was that high school flamethrowers aren’t a great investment — these prospects were half as likely as college pitchers to make it to the big leagues. Oakland A’s then-general manager Billy Beane famously announced his disdain for prep pitchers by smashing a chair through a wall when his scouting director took prep hurler Jeremy Bonderman.

As this year’s draft begins Monday, it might seem like the Minnesota Twins should bypass high school sensation Hunter Greene and use the No. 1 pick on Vanderbilt righty Kyle Wright. But the best practices for nailing the draft are constantly shifting. “Moneyball” once upended conventional baseball wisdom, but after more than a decade of stat-savvy teams heeding the lessons of early draft studies, the sabermetric takeaways have changed. These days, it might be college pitchers like Wright who are the bad bets.

There’s evidence that by the time “Moneyball” came along, teams had already begun to learn from their early draft mistakes. Baseball Prospectus’s Rany Jazayerli picked up on this fact way back in 2005, while researching what remains perhaps the deepest statistical dive into draft history ever conducted. Like Lewis, Jazayerli found that college prospects consistently made the majors more often than high schoolers, but Jazayerli also observed that the collegians’ once-huge advantage in value⁴⁴ shrunk significantly between the 1980s and 1990s. As Beane was chewing out his scouts for their excessive love of high school prospects, high school prospects were slowly becoming undervalued.

That trend has only gained steam in recent drafts. In the spirit of Jazayerli’s original study, I used data from TheBaseballCube.com to look at the first 100 players taken in each draft since 1965.⁴⁵ For each draftee, I tracked how many WAR⁴⁶ a player generated in either his first six seasons of MLB service time (the period during which a player is under team control) or the decade after his draft year.⁴⁷ Among those top-100 picks, there’s a clear relationship between where a player is drafted and how many WAR he’s worth during his pre-free-agency seasons:

Given the expected value of each pick, we can judge whether each type of player — hitter or pitcher, high school or college prospect — delivered on the investment teams made in them.

If we break things down into the same blocks of drafts Jazayerli looked at in 2005,⁴⁸ we can see that high schoolers have been quickly closing the gap that Beane was so worried about. From 1992 to ’99, the edge in value generated by college draftees at all positions was down about 60 percent compared with the same number from 1984 to ’91. And in the most recent group of drafts — featuring players whose pro careers came entirely in the 21st century — the average high school pick has produced essentially the same WAR (adjusted for draft slot) as the average college prospect. That’s the very first batch of drafts where college and high school draftees have played equally well, relative to expectations.

This change reflects the way front offices’ draft strategies have shifted over time, particularly in the post-“Moneyball” era. As other teams followed Beane’s lead and made selections guided by research about past drafts, the number of picks devoted to college players at all positions rose compared to previous batch of drafts. But that, in turn, caused college prospects to become overvalued, and, starting in the ’90s, they began delivering fewer returns than before. Although college hitters still appear to be far better bargains than high school ones, college pitchers have gone from being the draft’s best-kept secret to being a terrible investment. At the same time, their once-maligned high school counterparts have become more valuable.

In other words, the sabermetric draft wisdom of yesteryear had an expiration date, and even now, the rules continue to change. Recent drafts, which included such stars as Buster Posey (Florida State), Bryce Harper (Southern Nevada) and Chris Sale (Florida Gulf Coast), could end up turning the tables back in the collegians’ favor. (Then again, Mike Trout came straight out of high school, so maybe not.) That’s something to keep in mind when the Twins make their choice Monday. Should they pick Wright, or Greene? Or even University of Louisville’s first baseman/pitcher Brendan McKay? The most recent results say it’s now a toss-up whether high school or college prospects are more likely to pay off. But only time will tell which type of player the next generation of draft studies — and the GMs who rely on them — will endorse.