Minor League Stat Metrics
The Visual Guide to Minor Leaguers uses these metrics for basic stats in order to filter on quality. And in my stories, I color code those numbers green, blue, yellow or red in order to visually indicate quality.
Batters
Pitchers
Is there anything special about these grades? No, just a rough metric I have found useful for the leagues I am in. You are welcome to make your own measurements and levels.
One quick-and-dirty method you can use on any metric? Take your entire league player population and import it into a spreadsheet. Sort on that metric. See how many players there are in total, and divide them up into quartiles. Best quartile is your Excellent group, next quartile is your Good group, etc. It can be that simple.