July 24, 2012
It Happens Every May
It happens every May. Someone on your favorite team is having an uncharacteristically good (or bad) year. This year, David Wright got his groove back, while his former teammate Jose Reyes lost his way. Edwin Encarnacion and Carlos Ruiz started hitting home runs for no apparent reason. For a while, Albert Pujols (!) was stuck in a very public home run drought. Early in the season, analysts and fans have learned to (properly) dismiss these runs as small sample size flukes. They’re something to keep an eye on, but... he'll be back to normal soon.
And then, it happens. “Well, you know, we’ve reached the point in the season where sample sizes start to become meaningful. Smith has now amassed 150 PA, so we can really start to believe in his performance…”
What amazes (or perhaps just amuses) me is that the reaction to this magical point in the season is that fans start panicking, whether the player has been doing well or poorly. Fans of a poorly performing Smith go from wondering when he’ll revert to form to panicking over the fact that “he’ll… never… be… the same… again.” Fans of the surprisingly good Jones fall into despair because he's a one-year contract guy who will probably ride this to a three-year deal elsewhere. Why can’t baseball fans ever be happy?
That’s usually the point where I hear my name. “You see, there was this study done about when different stats start to stabilize, and we’ve gotten to the point in the season where we can say that this new strikeout rate that we’ve seen actually is what we can start to expect..." (And for the record, I am guilty of this too!) It’s just that there’s one tiny little problem.
That's not what the study was actually about.
There’s a giant assumption built into the statement “We’ve reached the point of stability so this is what you can expect out of Smith from here to eternity,” or at least for the rest of the year. It assumes that baseball players have fairly static talent levels over the course of a season. That's not an awful assumption. It may not even be a false assumption. But it’s an assumption, and assumptions must be challenged.