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Rockies’ pitchers might have a problem with the new baseball

Thin Colorado air + reduced drag = reduced pitch movement.

Arizona Diamondbacks v Colorado Rockies Photo by Matthew Stockman/Getty Images

I played my first game of Pokémon at the age of 35. I was in high school when Pokémon became popular, too preoccupied with mosh pits and girls to concern myself with HP and evolutions. Years later, my seven-year-old son decided he “gotta catch ‘em all.” He convinced me to play against him a few times, serving dual roles of teacher and opponent.

The problem is that seven-year-olds rarely play fairly. Either he made up rules as he saw fit, strategically withheld important information, or some combination thereof. I’ll never know the difference. I do know that I lost badly. It’s tough to win a game when the rules keep changing.

I’m not sure if Rockies pitching coach Steve Foster has ever played Pokémon against a seven-year-old, but he can certainly empathize with feelings helplessness and frustration. The physics of pitching in Colorado are neither fair nor consistent.

Rocky Pitching

The Rockies pitching staff was their strength last year, but has cratered in 2019. Their ERA and FIP jumped from 4.33 and 4.06 in 2018 to 5.39 and 4.82 this season. Of course, the whole league has gotten a little worse as well. However, adjusted stats like FIP- also show the team declined from 94 (eighth best in MLB) to 103 (17th in MLB). Individual pitchers have displayed drastic differences, such as Kyle Freeland’s ERA rocketing from 2.85 to 7.39 or German Márquez allowing a .602 OPS on the road and an .895 at home.

There could be many reasons for the drop-off, but the changed ball has to be one of them. Since Foster took the position in 2015, MLB has experienced wild fluctuations in scoring. Runs were down, then way up, then back down a little, and now ludicrously high.

As Dr. Meredith Wills explained for The Athletic, the baseball itself has changed significantly, causing wild differentials in home runs. Not only does the ball travel farther, but lower seams make it more difficult to snap off a breaking pitch, which in turn makes them more likely to hang in the zone and be well-struck by the batter.

Movement from pitches is generated by air pressure differential. If a pitcher grips and releases a pitch in a certain way, it will spin such that there is more drag on one side than the other. This creates less air pressure on one side, causing vertical and horizontal movement. If the seems are lower and pitchers can’t spin them as much, there is less pressure differential and less movement.

This creates a unique problem for Foster. While the ball is more challenging for pitchers all over MLB, there’s less air to begin with in Colorado. The thin mountain air compounds the difficulty of throwing a pitch with decent movement. The result is the slicker baseball is more devastating for the Rockies pitchers than other teams’.

Changes in Movement

Using Pitch Info data available on FanGraphs, we can compare horizontal and vertical movement of pitches year-to-year. Their have been 14 pitchers to throw at least ten innings for the Rockies both this year and last. By measuring how their average pitch movement has changed, we can see what affect the different baseball might have.

To clean up the data a little, we need to remove any pitch that a hurler used less than two percent of the time in either 2018 or 2019. This prevents any data skewing from pitches that aren’t really part of their repertoire or might have been miscategorized.

Here’s how pitch movement has changed since last season for 14 Rockies pitchers (X = horizontal, Z = vertical). If you’re so inclined, you can view the full spreadsheet here, including individual player data.

Rockies Pitch Movement Changes 2018-2019

Pitch Type # of Pitchers Pitch-X change (in.) Pitch-Z change (in.)
Pitch Type # of Pitchers Pitch-X change (in.) Pitch-Z change (in.)
Fastball (FA) 13 -0.5 -0.3
Cutter (FC) 4 0.0 0.1
Sinker (SI) 4 0.0 0.0
Changeup (CH) 9 -0.3 0.1
Slider (SL) 12 -0.4 -0.4
Curveball (CU) 8 0.5 0.0

We can see substantial movement decreases in fastballs and sliders. Heaters are moving 0.5 inches less horizontally and 0.3 inches less vertically. There are two pitchers (Tyler Anderson and Kyle Freeland) who have increased both types of fastball movement, but for ten others they lost both vertical and horizontal movement. Harrison Musgrave lost 0.3 inches horizontally, but has no change vertically.

The Rockies’ sliders are moving 0.4 inches less both horizontally and vertically. Two pitchers have lost at least 1.5 inches horizontally (Musgrave and Bryan Shaw), while four lost at least an inch vertically (Musgrave, Shaw, Jake McGee, and Jon Gray).

Both curveballs and changeups have very little change in vertical movement, but opposite changes in horizontal movement. Changeups are moving 0.3 inches less horizontally, while curves are dropping a half inch more. The individual data is noisy for both pitches though. There are few pitchers for both pitch types that had large gains and large decreases in vertical movement. If a couple of them altered their grips, for example, it would throw off our data.

Cutters and sinkers are used less frequently than the others, with only four Rockies using each of them. These pitches show almost no change at all on average, but there are differences in individual pitchers. Anderson’s cutter is moving 0.5 inches more horizontally and 0.9 more vertically. Shaw’s moves 0.2 inches less horizontally and 0.6 less vertically, so there is some offset. This is probably more indicative of the pitchers making changes than the ball and air quality impacting these pitch types.

Making Meaning

Fastballs and sliders are the two pitches thrown most often, and by the most number of pitchers. They’re also the two pitches with the greatest decreases in movement. A fraction of inch might not sound very substantial, but it can have a huge impact in launch angle and exit velocity.

Moving the bat-meets-ball contact point 0.3 inches vertically is the difference between a home run and a pop up, or a line drive and a ground ball. A half inch horizontally could be the difference between the sweet spot and the end of the bat.

These numbers are only averages and don’t include home/road splits. There are several other factors that could impact movement changes as well as the different ball, such as grip changes, injuries or other physiological alterations, and a few for which we probably can’t even account.

However, something is definitely different about the Rockies pitching staff this year. Given what we know about the changes in the baseball, that’s as likely a reason as any. Maybe Steve Foster should bring in Charazard out of the bullpen. That’s a Pokémon , isn’t it?


Daniel R. Epstein is an elementary special education teacher and president of the Somerset County Education Association. Tweets @depstein1983