The Effect of the Diamondbacks’ Humidor on Paul Goldschmidt

Since the beginning of last year when the Arizona Diamondbacks announced they would be introducing a humidor at their home park, Chase Field, there has been a lot of speculation as to how this would affect baseball being played. There is an expected reduction in overall offense as a result, but the question is just how much of a reduction. For those not familiar with the term, a humidor is a device that is used to control the humidity of the objects inside. Usually they are used to store cigars, but in this case this one will be used for Major League baseballs. The specific requirements for the Chase humidor will be 50% humidity at 75 degree Fahrenheit. Alan Nathan, a baseball physicist, took a look at this in an article for The Hardball Times and concluded that there would be a 25-50% reduction in home runs at Chase Field. This is definitely a substantial percentage and with news of the humidor being installed officially for the start of the 2018 season, the fantasy community has been fading Diamondback hitters and talking up Diamondback pitchers. I have been wondering for sometime if this was an extreme reaction to this news and if there was a good way to determine this. Up until recently, I was not sure, until I read an article that gave me an idea for this totally not scientific method feature below.

The article in question was written by David Kagan, also at The Hardball Times,  and provides us with a more concrete idea of what the effect humidity can have on a hit baseball. Kagan found that a ball at 0% humidity would travel approximately 14 ft farther than a ball at 50% humidity due to the additional mass of the ball from the moisture within. For me to examine each home run hit by a batter or given up by a  pitcher in Chase Field and apply a reduction to its distance would take a very long time because as far as I am aware, there was no easy way for me to access that data without building a set manually myself. While I could do this, and still might, I decided to focus on the star of the Diamondbacks, an underrated Major Leaguer (playing for a baseball team in Arizona will do that to you), a fantasy stud, and one of my favorite players, first baseman Paul Goldschmidt.

Now Paul Goldschmidt is a top option for any fantasy roster (unless your league rules make you want to grab unproductive players) and has been ever since 2013. This year he was a top choice to go 3rd overall in most fantasy leagues, after Mike Trout and Jose Altuve of course, but once news of the humidor officially being implemented broke, his fantasy stock has fallen.  His National Fantasy Baseball Championship, the most competitive high stakes fantasy leagues, (NFBC) Average Draft Position (ADP) through January 13th was 3rd overall with a high pick of 2 and a low pick of 7.  However, from January 13th until March 13th, he has become the 5th player overall taken in drafts with  a high pick still of 2 and a low pick now of 17. This is quite a change for someone who has been nothing but consistent the past four seasons and an all around producer.

As to his projections, certainly you could just remove 25-50% of his home runs for 2018, as well as other Diamondback hitters, and call it a day. However, I wanted to look for myself to determine if this reaction is over blown and maybe there was an opportunity to get these players at a discount in drafts. As a result, I came up with this totally not scientific method of determining what effect the humidor would have on Goldschmidt’s home run total in previous seasons. Thanks to Statcast data, I was able to view a variety of information on all of Paul Goldschmidt’s home runs at Chase Field over the past three seasons (they had some info on his previous seasons, but Statcast did not go live publicly until 2015). I was able to gather the distance traveled by each home run as well as a video, for most home runs, detailing the exact location in the park the ball was hit. This combination of data is important because outfield dimensions are not uniform throughout a ballpark. Essentially a ball hit 400 feet to dead center is an out when it would be a home run anywhere else in the park.

Therefore, thanks to Kagan’s work, I have the starting point for this experiment. With balls being stored at 50% humidity, the worst case scenario would be a drop of 14 feet on the distance of each home run, that is of course assuming an original humidity of 0%. This is not realistic though since the average humidity of Phoenix is approximately 20% (stated by Nathan in his article) which, with some simple proportional math, gives us roughly 8.4 feet of reduction in batted ball distance. Looking at the historical average daily humidity of Phoenix the past three years during the baseball season (end of March through the beginning of October), I actually found the humidity to be roughly 27.7% which would lead to approximately 6.2 feet of reduction in batted ball difference. Now armed with this knowledge, I decided to apply a reduction in feet to each home run he hit and determine if it would still be a home run.  To be specific, I reduced the distance by 14 feet to have a worst case scenario (In reality, it could be way worse, this is all theoretical at this point) when examining the home runs even though based on the findings, the reduction should be less. I summed up my results into the table below.

Author’s Note: I am still figuring out how to format tables in WordPress so instead of delaying this post even further, I figured I would come back and update the look of the table at a later date (or not).

Goldschmidt has hit 93 total home runs over the past three seasons with 48 of those ( 51%) coming at home in Chase Field. Based on what I found, only 26 (54%) of those were definitely still home runs after the worst case scenario which is 1) within Nathan’s projected reduction in home runs and 2) way less of a number than I expected. However, of the 22 remaining home runs, only 9 would be classified as definitely not home runs as those taters (one of the many slang words for home run, possibly the best) were only wall scrapers or hit far to a deep part of the ballpark. The final 13 home runs fall into a category I call SchroDingers (coined by me based on the paradox  Schrodinger’s cat. Dinger is another term for a home run, would you believe I almost published this calling them Schrodinger’s Home Runs? ) because until we know the exact impact the humidor will have on batted ball distance, these hits could be reclassified as a home run or not. The taters in this group were not quite wall scrapers, but depending on which reduction we apply may or may not be reclassified. The second table below contains the updated home run totals with the inclusion of away games to provide context for what the new total woulds look like for the season.

The table above compares Goldschmidt’s historical home run total to three possible scenarios if the humidor was in effect during those seasons. Over the past three seasons, Goldschmidt’s 93 home runs puts him at 19th overall (Nelson Cruz is the tater king over this period with 126). The worst case scenario assumes all the SchroDingers  were not classified as home runs and only the definite taters were kept. A total of 71 home runs moves him into a tie at 47th overall with Miguel Sano and Evan Gattis. Conversely, the best case scenario assumes all the SchroDingers remained home runs and were kept along with the the definite taters. In this scenario, Goldschmidt would move to sole possession of 23rd overall on the home run list just behind Jose Bautista. The average scenario (There has to be a better name for this) just assumed 50% of SchroDingers were still home runs.

While Nathan postulated a 25%-50% reduction in home runs at Chase Field thanks to the humidor, the worst case scenario for Goldschmidt over the past three seasons indicated he would only lose 24% of his total home runs. I was honestly not sure what I expected the results of this to be. On one hand, I sort of expected Goldschmidt to be one of the players least impacted by the humidor (I make the assumption he is based him being on the low end of the reduction). On the other hand, a 24% reduction in home runs is still pretty large as that is anywhere from 6-10 home runs a year he is not hitting which not only affects his home run count, but also his triple slash line (batting average, on-base percentage, and slugging percentage) and counting stats (specifically runs and runs batted in (RBI)). Those lost home runs have a chance to impact a few games over the course of a season. However, just because a ball does not clear the fence does not mean we can assume it is an automatic out. In addition, it is not only Paul Goldschmidt who will be affected by the humidor, but all of his teammates and opposing teams who play at Chase Field so everyone will be on an even playing field as far as real baseball is concerned. As for fantasy, I can see now why Goldschmidt’s ADP has dropped as his production should see a decrease solely due to the humidor. Nonetheless, he is an elite baseball player that is not just a reliant on home runs for value. He is definitely still a first rounder and probably still a top 7 pick for me in standard fantasy drafts. However, I think the fantasy community is right to adjust for the humidor heading into the 2018 season.

Original post on IVthoughts.com. Data taken from baseballsavant.com and Fangraphs.com. Links to referenced articles included above.