While I continue to pour through mounds of Gameday data from Minor League games, I thought I’d stop and share some numbers. I haven’t found a “story” that’s compelling enough to write about yet. Nor have I finished running through the numbers.
In a nutshell, I compared “year 1” and “year 2” performances for all pitchers who faced at least 200 batters in one league in 2007 or 2008 to the same pitcher in another league in 2008 or 2009. For example, Joe Schmoe if pitched in the Southern League in 2007 and the International League in 2008, he goes into the pool. There’s all sorts of problems with this approach, namely I’m not filtering pitchers who may have had substantial experience at a higher level during “year 1”, but it does give some idea of how guys progress.
A pitcher with a 50% ground ball rate in the Southern League (Double-A) would project to a 45% rate in the following season in the Pacific Coast League (Triple-A). A 40% rate projects to 37% and a 60% rate to 53% (y2 = y1*.7702 + .0656; r2=.4693). This ignores any information other statistics may provide in projecting ground ball rates. It does, however, let me split players into some cohorts (out- or under-performed) to carve out some case studies and start digging up those key individual differences that muddy the statistical waters. In this particular group, outliers included Max Scherzer, Esmerling Vasquez and Greg Miller, for whatever that’s worth.