We get it—the Rockies play at one of the best hitter’s parks in baseball history. That fact is one of the main talking points about the Colorado Rockies as well as one of the main arguments against Rockies players to win MVP or be elected to the MLB Hall of Fame.
But it’s not the only hitter’s ballpark in the National League West. Chase Field is quite favorable to hitters as well, so much so that the Diamondbacks intend to install a humidor, clearly inspired by Coors Field. But what are the differences between Coors Field and Chase Field, as far as hitter’s parks go?
Altitude is a big part of the “why” of Coors and Chase as hitter’s parks. Altitude is the big factor that affects hitting and pitching performances in both places, and there’s really no changing it, humidors or not. Coors Field sits at 5,186 feet above sea level and Chase Field sits at 1,061 feet. While that is a huge difference, Chase Field is the second highest field in Major League Baseball and is 119 feet above the next highest ballpark. In fact, the average altitude of all 30 ballparks is 509.77 feet. Without Coors or Chase, that number drops to 323.07 feet.
According to Clifton Neeley’s “Neeley Scale,” which measures air density at different altitudes on a scale of 1-100 with 1 being high altitude on a warm day and 100 being low altitude on a cold day, Coors Field usually sits between a 36 and 47, whereas Chase Field is closer between 54 and 62. Petco Park in San Diego is usually between 63 and 75. On a typical summer day, Coors Field has an air density index of 41.98 and Petco Park has an air density index of 64.07. If you convert these data into the typical air density units of kg/m^3, Denver has an air density of .966 kg/m^3 and San Diego has an air density of 1.182 kg/m^3. This means that two identically hit baseballs would travel about ten meters (approximately 32.8 feet) further in Coors Field!
On top of making it easier to get a hit, air density also makes it more difficult to pitch. It’s no secret that breaking balls don’t break across the plate as much as they would at lower elevation ballparks. According to the Neeley Scale, a 90 mph slider in a field like Petco would move about eight inches down and five inches side-to-side whereas the same pitch in Coors would move six inches down and three inches side-to-side. In Chase Field, it would move seven inches down and five inches side-to-side. Combine this with two of the largest outfields in baseball and it becomes really easy for hitters to earn extra bases and score more runs.
Park factors are the “what” of hitters parks. They show how favorable a given park is for pitchers or hitters. According to MLB.com, ballpark factor is defined as “runs scored by Team X (and its competitors) in Team X’s home ballpark and divides the figure by the runs scored by Team X and its competitors in Team X’s road contests.” As a mathematical formula, it is simply: ((homeRS + homeRA)/homeG)/((roadRS + roadRA)/roadG).
A park factor of 1.000 is a neutral park, and anything above favors hitters and anything below favors pitchers. In 2017, Coors Field ranked number one with a park factor of 1.332 and Chase Field ranked number three with a park factor of 1.202 according to ESPN. Petco Park ranked number 29 with a park factor of 0.828. In 2017, the most neutral park was Guaranteed Rate Field, home of the Chicago White Sox, with a PF of 1.003.
This statistic is used to determine which stadiums favor hitters and which stadiums favor pitchers. The biggest issue with this is that it does not account for pitching on each team, which can skew the PF if they are above average to make certain parks seem more pitcher friendly than they really are. This can be shown by the fact that 1.332 is the lowest PF at Coors Field since 2013, when it posted a 1.273. It was still the top ranked park at that time, though. This can also be shown in the fact that in 2013, the Diamondbacks posted a 0.974 PF, which would make the park seem much more pitcher friendly. The team still went 81-81 and missed the playoffs that year. Here is where each park has ranked since 2009:
Coors Field and Chase Field Ballpark Factor 2009-present
The Hits that Fall
As a result of these two factors, both the Rockies and Diamondbacks get boosts to their offense at home. Think of the outcomes as the “how” of what makes Coors and Chase hitters’ parks. Since 2009, the Rockies have averaged 27.9 more home runs, 53.1 extra base hits, and 49 points higher in BABIP at home than away. In that same time period, the Rockies have also averaged 11.7 more home runs, equal extra base hits, and 8 points higher in BABIP than their opponents at Coors Field.
Since 2009, the Diamondbacks have averaged 10 more home runs, 37 extra base hits, and 21 points higher in BABIP at home than away. In that same time period, the Diamondbacks have also averaged two fewer home runs, 9.1 more extra base hits, and five points higher in BABIP than their opponents at Chase Field.
This shows two things: 1) the Rockies and Diamondbacks definitely have an advantage at their home parks than on the road and 2) while Coors and Chase are both reliably hitter’s parks, the Rockies have a much more dramatic split. A big part of that is likely due to the topic we started with: Coors Field is 4,125 feet higher in elevation than Chase Field.
The altitude of both of these ballparks makes it harder for pitchers to pitch and easier for hitters to hit and park factor reflects that every year. Even though Coors Field has annually topped the charts in offensive categories, Chase Field isn’t far behind!
Within the last few years especially, the Rockies and Diamondbacks have been more similar than not in just about every aspect. In three out of the last nine years, Coors and Chase have topped the ballpark factor chart, and that goes to show that they are scoring a similar number of runs and also getting a similar number of runs scored on them. Specifically in 2016 and 2017, they both had similar pitching staff makeups as well as offensive and defensive numbers, which eventually led both teams to playoff berths in 2017.
These two teams with home parks that play relatively the same; they both look to be heading in to a contention window; and they, remember, faced off against one another in last year’s Wild Card game. Let’s see what these emerging rivals do in 2018.