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D-Backs MiLB Pitchers: Running the Gauntlet

Pitching in hitter friendly leagues and parks, are they underrated ?

Frisco RoughRiders v Amarillo Sod Poodles
Ryne Nelson, Amarillo Sod Poodles
Photo by John E. Moore III/Getty Images

During the season I posted comments and tables several times pointing out my concerns that the Diamondbacks pitching prospects might be getting overhyped and we might be putting too high expectations on them. However I started focusing on xFIP because it seemed like our pitchers were allowing more homers than would be expected, but I wasn’t sure why. The one big problem I had was that Fangraphs does not give us any park adjusted metrics for minor league pitchers, i.e. ERA-, FIP-, & xFIP-minus . They have wRC+ for hitters but no adjustments for pitchers.

When looking at these tables their performances seemed ok in many cases, but not eye popping. However over the last few days I’ve become more aware of information that mitigates some of my earlier concerns and raises my optimism somewhat. I’ll be circling back to those rankings at the end of the article. This is long, but try to stay with me because I think this is important not only when looking at 2021 performances relative to the rest of Minor League Baseball, but looking forward as well.

Of course we are talking about pitching prospects here, the most volatile types of player to evaluate, especially just using stats. So I’m not sure of anything, and nothing I write here should lead one to think I am. I’ve seen very little of these guys pitch. I’m just looking at stats and spread sheets. The team is obviously going to hype them, and we should take that with a grain of salt. But none of the Diamondbacks pitchers were ranked inside the top 50 by BA at mid season, (Blake Walston ranked 85, & Ryne Nelson ranked 98th). MLB Pipeline doesn’t rank any D-backs pitcher in the top 100, although they have Walston and Nelson 4th & 5th on D-backs top 30. I’m now wondering if they, (and I) may be selling a couple of them short.

The main issue I see is park factors and league run environments. At each level our pitchers toil in the most hitter friendly leagues for that level, and most often in hitter and especially HOMER friendly ballparks within those leagues. We’ll be taking a close look below, but first some important information and caveats. The league data is pulled from Baseball Reference Register. The park factors come from Baseball America. (Subscription required, but well worth it and quite essential if you have any interest at all in the minor leagues and prospects) Matt Eddy, executive editor of BA said to me about the park factors:

Use these park factors as a guidepost but know that 2021 was truly a season unlike any other in minor league history.

Indeed, there are many factors in 2021 that are quite different from years past. The number of teams in the league is one. Some leagues have just 6 or 8 teams, while others have 10, 12 or even 20. The Covid-19 Pandemic impacted these factors as well. One example is the High A West league, where the Hillsboro Hops had to share their ballpark with the Vancouver Canadians, who used the Hillsboro stadium as their home ballpark all year. But Hillsboro and Vancouver have very different park factors, (Vancouver much more pitcher friendly) and these factors don’t actually deal with the fact that each team played a good number of “road games” in their home park for the year. Add to that there are only 6 teams in that league, and it’s messy, to say the least. There are other examples, such as Buffalo needing to play their games in Trenton NJ through July, until the Blue Jays finally cleared out and were able to resume games in Toronto. These are just a few examples.

So with those caveats, lets take a look at the various leagues by level and the Diamondbacks ballparks specifically:


NOTE: 100 = Neutral, above 100 favors hitter, below 100 favors pitcher

The AAA West is comprised mostly of old PCL teams with a few former Texas League teams thrown in. But there are only 10 teams, compared to AAA East which has 20. This setup was done to reduce travel obviously, as that reduces Covid Infection risk, however as you can see the 1 Run per game difference between the East and West and 67 points of OPS are huge. Somewhat surprisingly perhaps, Reno was not even the most hitter friendly park this year. Las Vegas, El Paso, and Albuquerque all ranked more hitter friendly. But suffice to say “The Reno Effect” will continue to be in play when attempting to evaluate Diamondbacks pitcher and hitter performance.


While not quite the hitters league the AAA West is, the AA Central where the Amarillo Sod Poodles play is clearly the most hitter friendly AA League. But that’s not the headline. Just take a look at the HUGE park factors for Runs (127) , Homers (169 !!!), and BABIP the pitchers in Amarillo have to deal with. While I’m not at liberty to publish the entire league’s park factors without infringing copy write , suffice to say the gap between Amarillo and the next most hitter friendly park in the league is very very large. Jim alluded to this yesterday by the way, mentioning the 3600 ft. elevation.

This is a pretty big problem in my view. In the past the D-backs had more pitching neutral environments for their AA pitchers making it easier to evaluate before they faced the crucible of Reno and the PCL. Obviously the flipside is true when evaluating hitters. Just like we tend to mentally adjust Reno hitting stats even before looking at metrics like wRC+ , we might need to be doing the same “discounting” in our minds when viewing Sod Poodles hitting numbers. While the nature of these park factors are to function as a guidepost, rather than being viewed as etched in stone, these are so extreme as to give me a great deal of concern going forward. By the end of 2022 will we be talking about “The Amarillo Effect” too?

High A

The High A West League is not overly hitter friendly, going by OPS. At this level you start to see higher walk rates and lower Fielding Percentages, which contribute to the R/G avg being a bit high, but that’s mostly younger pitching and defense. As mentioned above, it’s tough to evaluate park factors here, but between Hillsboro and Vancouver stats, it appears this stadium played pitcher friendly relative to the rest of the league.


The Low A West League is comprised of former California League teams, and is another extreme hitters environment compared to the parks in the East and Southeast. Furthermore, while Visalia was neutral for runs, it played as a homer and hit friendly park relative to the rest of the league.

Complex Leagues

Even the Arizona Complex League is more hitter and homer friendly than the Florida league.


The table below is looking at Diamondbacks pitchers that had at least 50 IP in 2021, with a sizable chunk of their innings coming as a starting pitcher. The table may be missing a few guys you are interested in, including guys that didn’t get to 50 IP due to injuries or being pure relievers. But I’m trying to evaluate starters here.

There are 580 minor league pitchers that had over 50 IP with at least 14% of their games, or 25% of their innings as a starter. Arbitrary cutoffs by me to be sure. What I did was take the average of ERA/FIP & xFIP, and also the average rank among 580 minor league pitchers to show where D-backs starters ranked. Based on the park factor information above, if Fangraphs were to ever create park adjusted pitching metrics for minor leagues, the Diamondbacks rankings would surely improve. Just how much I’m not sure, but probably at least 5-10%, maybe more in a few cases.