Does Pedigree Matter?
Ben Zobrist was a sixth-round pick who had done nothing special in the first three years of his Major League career, but then put up one of the best seasons in baseball in 2009. Ryan Zimmerman, the fourth overall pick of the 2005 draft, put all the pieces together and became one of the best players in baseball in 2009. We perceive them differently mainly because Zimmerman is a much better player, but the point I'd like to make is that their original draft status--their pedigree--also factors into how we think of these guys. Should it affect our projections going forward?
Projections are hard. Instead, I broke players into three groups depending on whether they surpassed their previous year's WAR, fell short of their previous year, or they didn't play at all. Data courtesy of baseballprojection.com. And using Retrosheet, I broke players' pedigrees into five grades. Top 10 draft picks, rest of the first round, second-third rounds, third-tenth rounds, and anything after that.
As you can see below, from the first year in the Majors to the second, first-round draft picks (the As and Bs) have a much higher improvement rate than lesser prospects.
There are a lot of things going on here. First of all, The better prospects are younger, and are therefore more likely to improve. Also, The better prospects are given more leeway to fail, so there is a much lower percentage who do not play in the subsequent year. And yes, I think that at this point, they are probably better players than their counterparts, production being equal.
How about year two to year three?
More of the same. Higher pedigree players are still improving at a higher rate.
This effect is starting to appear consistent. Let's keep going.
We need until the fifth year to see pedigree becoming negligible.
Controlling for the quality of the player by creating a projection is necessary to make any conclusions. Nevertheless, I think the matter warrants further consideration. Projection systems are sometimes built to use data as far back as college, but I haven't heard of any that include draft position, really the only prospect grading system for which there is a large volume of discrete data. A draft pick provides a snapshot of what up to 30 MLB teams all with presumably independent and sophisticated thought processes thought of a single player at a single time. That picture fades, but even when a player makes the Majors, it's still part of his history.