Doctoring the Numbers: Starting Them Young

Baseball Prospectus co-founder Rany Jazayerli returned to BP on October 13, 2011, for a series on player development and the amateur draft:

Everyone missed on Mike Trout. Don’t get me wrong: Trout was a well-regarded player headed into the 2009 draft, a certain first-round talent. But he wasn’t—yet—a phenom. Everyone liked Trout; it’s just that no one loved him. Baseball America ranked him as the 22nd-best player in the draft. No one doubted his athleticism or his work ethic; a lot of people doubted the level of competition he faced as a high school player from rural New Jersey. The Angels drafted him with the 25th pick overall, and they’ll tell you today that they knew he was destined to be a special player. What they won’t tell you is that they had back-to-back picks at #24 and #25, and they announced Randal Grichuk’s name first.

It didn’t take Trout long to prove to everyone that he had been underestimated. … In Trout’s case, there’s one astoundingly obvious reason why he was underrated going into the draft. It’s one of the most basic pieces of information we have about a player, a piece of information that precisely because of its ubiquity is almost always ignored: his date of birth.

Mike Trout was born on August 7, 1991. This is relevant because, unlike most players drafted out of high school, Trout was still just 17 years old when he was picked. His performance as a high school senior came at an age when many of his fellow draftees were still in their junior year; he played as well as he did without the benefit of an extra year of development.


Here’s my point: I don’t think anyone would argue that, all things equal, a 17-year-old player is likely to develop into a better player than an 18-year-old player. But I wondered if the baseball industry as a whole has underestimated the importance of age. I wondered if, given two players taken at the same slot in the draft, the younger player returned greater value. In other words, even accounting for the fact that teams took age into consideration—presumably, a player who is particularly young for his draft class might get picked earlier—I wondered if those players were still undervalued. So I decided to do a study.

Read the first part of Rany’s study here:

Read the second part here:

Originally published: October 17, 2011. Last Updated: October 17, 2011.