After a few years of neutrality, 2024 saw a sharp spike
This was initiated by the Dodgers winning the Silver Slugger team award yesterday. It seemed weird, considering the D-backs scored 44 more runs then their divisional rivals. But in the discussion on Reddit, it was suggested this was simply because Arizona played in a much more hitter-friendly park. This went against what felt like generally held wisdom. Two years ago, Jack stated, Chase Field is No Longer A Hitter’s Ballpark, and the evidence at that time seemed to back it up. The introduction of the humidor and the artificial turf had severely reined in the effects of the altitude (it being the second-highest park in the majors) and the dry atmosphere. At the time Jack wrote, Chase Field had a park factor of just 98.
We should explain how park factors are calculated and what they mean. There are a couple of different approaches, but they are all bases around a 100 score being average. Higher than that means the park favors hitters; lower than that, it favors pitchers. So the 98 score mentioned, indicates Chase Field was slightly pitcher-friendly. The calculation used by Baseball Reference is based on runs scored and allowed, at home and away, by each team. Baseball Savant appears to take an individual-based approach: it “is generated by looking at each batter and pitcher, controlled by handedness, and comparing the frequency of that metric in the selected park compared to the performance of those players in other parks.”
Now, these numbers are subject to fluctuations. Both sources like to take a three-year average to come up with figures, which mutes the randomness. This makes sense, because even in consecutive years with exactly the same ballpark conditions, output will vary, both on an individual and team level. So you should not over-react to a single year’s numbers, whether higher or lower than “normal”. It’s possible they may simply be the result of these variations, and next year the park factor may revert back to being where they were. On the other hand, you can’t just write them off. A change may be the ‘canary in the coalmine’, the first reflection of a change in environment.
With all that said… You would probably be surprised to hear that, based on 2024 results alone, Chase Field trailed only Coors Field in Baseball Savant’s Park Factor, with an overall value of 106. That’s a sharp uptick in the 2023 figure which was only 99. The latter is the sort of range in which Chase has operated since the introduction of the humider, before the 2018 season. In 2017, the last year pre-humidor, Chase had a Park Factor of 105; the following season, it dropped to 100, and has operated in less hitter-friendly fashion than 2017 every season since, with a Park Factor mostly in the range of 98-100. B-R has a smaller uptick, with a one-year batting figure of 103.
One of the benefits of Baseball Savant is that it breaks things down to individual events. For example, a venue with a large outfield could reduce the number of home-runs, but all that terrain might lead to an increase in triples. Changes that affect one event can lead to an increase in another. When the humidor was introduced, that happened in Chase Field: the number of home-runs dropped by over twenty percent, declining from 205 to 161. But not all of those became outs: the number of triples increased by 10%, year to year. The nooks and crannies in Phoenix have kept the park triple-friendly ever since. Indeed, no NL stadium saw more three-baggers than Chase this season.
This colorful chart lists the Statcast Park Factors for Chase each year, so you can break it down and see what led to the large jump in overall PF for 2024. You can see the two categories which really increased in 2024 were doubles and home-runs. The former may be one of those random glitches I mentioned above. In 2021 the double PF spiked from 105 to 129, but then dropped back to 108 the next season. If that had happened after 2018, when the artificial turf went it, it might have been significant, but I can’t think of any reason that would trigger such an increase for 2024. The home-run increase might be more interesting, though Chase Field still isn’t what it used to be.
That’s because it was almost the worst park to hit home-runs in during 2023, with a PF of 79 – ahead only of PNC Park in Pittsburgh and Progressive Field in Cleveland. This season saw an uptick of thirteen points to 92, but still left Chase only 21st. It’s a far cry from the pre-humidor days, when balls flew out of the downtown park at a rate typically ranking it among the top five venues in the majors. The HR PF figure is now comparable to that in the early humidor days (2018-20), but just about all other hits are now higher than they were. The overall result sees the Runs PF this year at 112 – higher than it was even in the last season before the humidor.
If this is a genuine change, then it perhaps means that the D-backs’ offense wasn’t quite as good as it seemed on the surface, scoring more runs than any other team in the majors. Even the numbers that take park factor into account, such as OPS+, will tend to do so based on the multi-year PF. Should this be “the new normal” going forward, it means those figures will underestimate the park factor, causing Arizona’s offense to look better than it was. I must admit, I did wonder how we had an OPS+ of 115, seventeen points better than in 2023, despite a lot of the same personnel. Joc Pederson can only do so much. 🙂
To be clear, I’m certainly not claiming this is a permanent change. One possible theory is it could be a result of the well-documented problems with the air-conditioning at Chase. It’s been estimated that every 10 degrees increase in temperature adds 1% to distance. As a counter-argument, the average temperature at Chase was actually a degree lower this season. But also known are the sharp discrepancies in temperature at different locations in the ballpark. Being cooler at home-plate doesn’t necessarily mean the same applies to the air through which a fly-ball travels on its way to the outfield. So, it could be a factor. We just don’t know.
And that last sentence is probably the best one to take away from this article. For now, these numbers are simply interesting, and should not be considered significant on their own. However, it’s something to keep in your back pocket with regard to next year. I’m curious to see how the figures stack up at Chase Field in 2025. If they remain at the current level, then we might have to begin to rethink our position, with regard to whether or not it is a hitter’s park.