January 14, 2013
Does Having a Veteran Around Help Young Players?
Last week, I wrote a piece on the social development of young baseball players (and humans in general). In the piece, I suggested that one reason that teams might employ older players who are well past their prime, to the point where they are barely replacement level, is that there might be something to the "clubhouse guy" effect, particularly on young players. Players in their early 20s are going through a seldom recognized and only recently understood period of neurological development, and in addition to being baseball players are also trying to figure out how to be adults. There might be some value to having a guy around who is... well, already an adult. Someone who could take a young player under his wing.
When I wrote that, I was thinking mostly in terms of the minor leagues, particularly for the age 18-21 set. During those early years, a player might need guidance not only on how to hit a curveball, but also on how to be a fully-grown man. An older player who has been there might be a good person to approach. Teams often talk about older veterans in terms of their possible contributions to the team off the field, even at the major-league level. Those guys are a calming influence in the clubhouse. They help keep the younger players focused.
Well, if I'm going to propose a theory like that, I should be willing to test it against the evidence. In the past, I have found some evidence that older catchers may help young pitchers in a meaningful, if minor way. Does it work for hitters?
(As always, if you think math is witchcraft, please skip the next section and go to "The Results.")
Warning! Gory Mathematical Details Ahead!
Let's define some terms. I looked at all players under the age of 25 from 1993-2011 who had 250 PA in a season and also in the season before. I calculated their on-base percentage for both years, determining the change between years using the standardized method that I have described before. This method controls for differences in the reliability of a statistic given different sampling frames (i.e. OBP, like any stat, is more reliable after 500 PA rather than 250 PA) and produces a z-score to tell how much a player has changed over time. Only players who remained with one team all year were eligible (although a player might change teams between years).