One potential problem that could arise when using the prior three years as your
data base is how to project those players who have played for different teams
or in the minor leagues. Thanks to the excellent work of Bill James, this was
not a problem for offensive players.
For those of you not familiar with his work, he created a series of formulas which convert minor league stats to "Major League Equivalents". The purpose of this essay is not to go into a treatise on how they work, that has been done more extensively by Mr. James himself. For these purposes you just need to know that we use them and that they are accurate enough to be used in arbitration hearings.
In 1988 we created a set of conversion formulas for pitchers. While Mr. James said this could not be done, a couple years after we had done so he came out with his own conversion formulas for pitchers. As with major league pitchers and hitters, the minor league pitchers are not as predictable as the hitters, but they are as predictable as major league pitchers.
Over the years we have sharpened our formulas. For example, Mr. James suggests increasing the production of players under 28 and decreasing the performance of players over 30. As noted in our other essays on Historical Performance and Peak Years we have found that these age ranges do not hold true in every category. Thus, we tailor the ages when players are improving or declining to particular categories.
IMPORTANT
The most important thing to remember with MLEs is that they show a player’s propensity to perform in given categories WHEN HE IS READY FOR THE MAJOR LEAGUES. It is not necessarily an indication of how he will perform in the upcoming season.
What, you may ask, is the difference? The difference is huge. For players at the AAA level, the MLEs are essentially what he is capable of doing in the major leagues today. The MLEs from AA and below show what he will be capable of in the major leagues with continued instruction and experience. If a team "rushes" a player to the majors, he may be "beaten up" for a while until his experience catches up to his level of play.
These conversions account for most of the work that we do in the off-season to prepare the system for the next year. Most of you love our rookie projections and this work and attention to detail is why.
Another deviation we have from Mr. James is that he converted players by looking at their stats compared to the stats of his teammates in that park in that year. What we have done is to use a ten year history of each minor league ballpark (when available) rather than the stats put up that one year. What this does is smooth out the glitches inherent in the particular make-up of a minor league team. For example, if a ballpark is traditionally a hitter’s ballpark but one year that team has a tremendous pitching staff, if you only looked to that year you would over-inflate the production of the hitters and undervalue the production of the pitchers because you would think the park was a pitcher’s park.
A good example from the major leagues is
We hope you have found this discussion useful and we would love to hear from you on any thoughts you may have about converting minor league statistics.
Return to Strategic Essay List
Return to PPI Home Page
Email questions to PPI or email
support@stallvalue.com
Copyright (c) 2004 Player Projections, Inc. All rights reserved