Can spring training slugging really predict a breakout season?

From SABR member Ben Lindbergh and Jon Shepherd at Baseball Prospectus on April 3, 2013, with mention of SABR member John Dewan:

It’s only natural to seek meaning in spring training statistics. By the time spring games roll around, we’re baseball-starved enough to believe anything. We’re also preparing for fantasy drafts, which means we’re always on the lookout for any info that could give us an edge. And contrary to the popular stathead saying, spring training stats aren’t actually meaningless—they’re just less meaningful, compared to a same-sized sample of big-league performance. Any change in a player’s performance should produce a corresponding (albeit small) change in our projection for that player. The more extreme that change in performance is, and the larger the sample, the more that projection shifts.

The most commonly cited method for assessing spring training statistics was proposed and popularized by John Dewan, the owner of Baseball Info Solutions. Dewan has devoted most of his analytical efforts to quantifying fielding, but he tackles other statistical topics in his “Stat of the Week” series at the website of publisher Acta Sports. Since at least 2005, Dewan has published an annual list of players whom he thinks stand a good chance to break out in the upcoming season, based on their spring training stats.

To earn a place on Dewan’s list, a player must (in most years, at least—more on that later) meet the following criteria:

  • He must have at least 200 career at-bats in the majors.
  • He must have at least 40 at-bats in the current season’s spring training.
  • His slugging percentage in the current season’s spring training must exceed his career slugging percentage by at least 200 points.

Conceptually speaking, this makes some sense: the more extreme a spring training performance, the more likely it is to be meaningful, despite the small sample. In recent years, the 200/40/.200 criteria, now known as “the Dewan Rule,” has become quite popular, with posts about potential breakout candidates popping up around the internet in anticipation of or in response to the appearance of Dewan’s list.

Read the full article here:

Originally published: April 3, 2013. Last Updated: April 3, 2013.