A few weeks ago I wrote a quick primer on a few general things to look for when analyzing minor league stats – and one of them was performance relative to league. Today, I’m going to go into how to view stats from each league in the minors with more detail (you know, like, numbers and charts and stuff). Trust me, you’ll like it.

First let’s start with the most basic of factors: runs. Here is a chart of the last three seasons (2010-2012) of minor league data for runs scored per game, broken out by league, courtesy of Baseball Reference:

This chart is pretty self-explanatory and presents a pretty self-explanatory idea of how to view the offensive environment of the different leagues across the minors. On the far left, you’ve got the high-scoring havens like the Pioneer, Arizona, California and Pacific Coast Leagues. On the far right, once you take out the American/National League (for reference), you have the Florida State, Gulf Coast and Carolina Leagues. To an extent this makes sense from a geographical standpoint – higher altitude and lower humidity creates higher offensive environments and lower altitude and higher humidity creates lower offensive environments. Also, the Florida State League plays in spring training parks with large dimensions and the Pioneer/California League both have many parks that are bandboxes, which only exacerbates the geographical issue.

Now we move on to the individual player stats that we look at in order to determine future value — after the jump…

There’s no one statistic that we all look at to evaluate minor leaguers, but HR and OPS are certainly two that are on my checklist. Here are two charts that you should see before evaluating a player off his numbers:

So let’s use a real life example from 2012. Here are two players with somewhat similar raw stats:

George Springer (California League, High-A): .316/.398/.557 with 22 HR, 82 RBI, 28 SB in 433 AB
Christian Yelich (Florida State League, High-A): .330/.404/.519 with 12 HR, 48 RBI, 20 SB in 397 AB

Excluding age relative to league from this particular case (Springer is 23, Yelich is 20), who had the more impressive season from a statistical standpoint? The answer is Yelich and it’s not particularly close. You can’t ignore that the average OPS in the California League is more than 70 points higher than in the Florida State League, or that home runs are hit nearly 1.6x more often.

This same concept goes for pitchers, the only difference is that the stats you’re looking at are less of an integral part of the analysis. If you’re looking at a pitcher’s ERA as the #1 stat in predicting future performance, you’re going about it wrong anyway (I’d suggest looking at K/BB/GB%/HR to start). But you’ll look at it anyway, and it can be deceiving. Take these two pitchers from 2012:

Player A in Triple-A: 3.66 ERA, 1.31 WHIP and 9.8 K/9 in 128 IP
Player B in Triple-A: 4.89 ERA, 1.47 WHIP and 10.4 K/9 in 130 2/3 IP

Right now you know nothing else about these players other than their stats. Both of them are legit prospects and both have seen time with their big league clubs this year (and had success). Before telling you who the players are, would you care to know that the average ERA for a pitcher in the Pacific Coast League (4.86) was almost a full run higher than in the International League (4.03)? Probably. As for further context here, Player A had a 46% ground ball rate in the International League and Player B had a 33% ground ball rate in the Pacific Coast League. So while it may be very tempting to say that Player A (Chris Archer) had a much better year than Player B (Shelby Miller), it’s a lot closer than you think.

Here is a chart by league for pitcher ERA:

Pretty much as you’d expect based on the rest of this post. One interesting thing I noticed when this chart came together is that, depending on the organization a pitcher is from, they could spend almost all of their minor league career on one side of the spectrum. Take Taylor Guerrieri of the Rays for example. He’s in the New York Penn League now, and if he moves up one level at a time, he would pass through the Midwest League, Carolina League, Southern League and International League – all in the lower half of the ERA spectrum. On the other hand, take Nick Tropeano of the Astros. He started his career in the South Atlantic League (which is right around average) and then moved up to the California League during the 2012 season. Things won’t get much easier as he moves up the ranks, as next up for him are the Texas League and Pacific Coast League – that makes three of the five worst leagues for pitcher ERA. But the more you know, the more you can use to your advantage.

I’ll be going through more examples of things like this throughout the off-season, although they will likely be more focused on prospects one-at-a-time. But until then, enjoy one last chart which I created strictly because I already had all the numbers in a spreadsheet in front of me already. Even wonder how much better defense really gets as you move up the ranks in the minor leagues? If so, this is for you:

Sometimes things look exactly the way you think they should.