Coors Field’s Impact on Pitch Movement

Coors Field has long been synonymous with offensive slugfests which give pitchers nightmares. In addition to this, we know that the higher altitude in Denver is what affects the baseballs’ trajectory as they are both thrown and hit. Often the “thin air” is brought up as what allows the baseballs to travel further in Coors Field, but this article will focus on the pitches before contact. I aim to build off of the article by Wyatt Kleinberg: Pitching at Coors Field, by looking at the 21 starting pitchers that have pitched at least 1 game at Coors Field and 1 game away from Coors Field in 2021.

After separating each pitch, I found that both horizontal and vertical movement were affected significantly based on whether or not the pitchers were at Coors Field. For every pitch, pitchers had less horizontal movement at Coors Field than elsewhere. The pitches that typically have more horizontal movement (sinker and changeup) were the ones that showed the biggest decrease in movement at Coors Field, while the pitches that had the least horizontal movement (Cutter and Slider) showed the least difference in movement at Coors Field. For Vertical Movement, it may seem that the results from each pitch tell different stories, yet they actually still follow a pattern. Fastballs have the largest difference (3.1 increase) which means they have 3.1 inches more drop at Coors or 3.1 inches less rise. Changeups ended up having about half as much difference as fastballs which is consistent with the data which had about double the vertical drop as fastballs. Because Curveballs typically have flipped spins of fastballs (i.e. topspin), I saw a negative value which means less break at Coors Field. Sliders and Cutters did not see much change which makes sense being that they are typically thrown around the 9:00 or 3:00 range where the ball just falls with gravity and is not affected as much vertically by the spin. In summary for vertical movement, Coors Field leads to less generated movement for pitches resulting in both a decrease in Fastball rise and less Curveball break.

After looking at the chart showing changes in pitch movement I wanted to make sure there wasn’t any drastic changes in pitch speeds or spin rates of the pitchers at Coors Field vs. elsewhere that may have affected the movement. I was pleased to find that both pitch speed and pitch spin were almost identical for every pitch at Coors vs. away from Coors. The biggest change in spin rate was a little less than 4% increase in sinker, while the biggest change in speed was a 0.5% decrease in fastball speed at Coors Field

I chose Houston as a comparison because the camera angle was the closest I could find to Coors Field’s angle. The ball that ends higher is the pitch in Houston, and the ball that ends lower is the pitch in Denver. With this article we can see that Coors Field not only adds distance to balls hit, but takes away pitch movement, thus making pitches easier to hit…Have fun pitchers!