The California League is a hitter’s league. The Florida State League is impossible to hit in. You can’t trust the stats for Rockies’ prospects because Asheville and Lancaster are so hitter-friendly. The hitters in the Eastern League were terrible last year. That prospect got ‘a big bump’ because he got to hit with the MLB ball at AAA last year. There are a lot of anecdotes like this used to qualify a hitter’s minor league performance.

But, why use an anecdote when you can create a stat to look at the concept?

Thanks to Sam Dykstra’s park factors work for MiLB.com, the league register pages from Baseball-Reference.com, and the downloadable minor league leaderboards from FanGraphs.com, we can account for and adjust for both league and park factors when looking at prospect statistics!

I can now do a quick statistical analysis of a hitter by looking at his league and park adjusted OPS+ and ISO+ at each level. Yes, I’m aware that OPS is ‘bad math’ compared to wOBA’s linear weights. However, I agree with the position that OPS gets the job done nearly as well as wOBA does, and it’s pretty easily understood even by casual baseball fans at this point.

Enough chatter, here are the stats. Presented below are league and park-adjusted OPS+ and ISO+ for each batting appearance of 100 or more PAs by a batter aged 25 or younger in full-season minor league baseball in 2019. They are presented as an indexed statistic, so ‘100’ equals average and each integer above or below 100 represents a percentage point of difference from the average performance (ex. Sam Huff’s ISO was 265% better than the average Sally League hitter in 2019):

2019 Minors OPS+ and ISO+