Mitchell: Forecasting major-league hitting with minor-league stats

From Chris Mitchell at The Hardball Times on December 30, 2014:

During the summer I crunched some numbers in the FanGraphs Community section aiming to figure out how a minor league hitter’s age and minor league stats can predict his future in the major leagues. I named my methodology KATOH after Yankees prospect Gosuke Katoh, who spent all of the 2014 season playing second base for the Class-A Charleston RiverDogs of the South Atlantic League. At the time, Katoh was running a strikeout rate close to 40 percent, but at just 19 years old, he was two or three years younger than most of his competition.

Katoh’s situation caused me to realize that I had no idea what was truly important in evaluating the performance of a player like him. Should I be worried that he’s striking out four out of every10 times? Does his respectable 12 percent walk rate make his strikeouts less a problem? Should I ignore the stats altogether and just give him the benefit of the doubt for even playing in full-season ball as a teenager? I hadn’t the foggiest.

To get a better sense of what mattered most, I turned to the reams of minor league data available through Baseball-Reference. Using these data, I ran some probit regressions, which tell us how a variety of inputs can predict the likelihood of an event that has two possible outcomes. For example, it might give the probability of a prospect’s making it to the majors based on his age and league-adjusted strikeout percentage, walk percentage, isolated slugging, batting average on balls in play, and frequency of stolen base attempts.

For this first iteration of KATOH, I looked exclusively at minor league hitters and estimated the probability they would play in the majors. This time around, I’ve expanded the system to slap a probability on a wider variety of outcomes–namely WAR thresholds–that a player might achieve through age 28. The thresholds I chose were loosely based on the 20-80 scale for overall value laid out by Kiley McDaniel.

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Originally published: December 31, 2014. Last Updated: December 31, 2014.