OC Register: What’s in a pitch? A Biola statistician connects a change in the baseball to movement

[AngelsWin.com]

In May, Major League Baseball commissioned a team of researchers to investigate the reasons for a spike in home runs that began in 2015. Their study concluded that the extra home runs could be attributed, in part, to a change in the aerodynamic properties of the baseball itself. The MLB-record 1.26 home runs per game in 2017 were helped by a renewed focus on launch angle, to be sure. But the baseballs helped too.

Maybe you remember the fallout that ensued. MLB committed to more stringent oversight of Rawlings’ plant in Costa Rica, where its baseballs are manufactured. Minor League Baseball announced that its two Triple-A leagues – the Pacific Coast League and International League – would begin using major league-quality baseballs in 2019. And while MLB’s committee couldn’t determine why the ball’s aerodynamic properties had changed, an independent study conducted by Dr. Meredith Wills suggested the laces had thickened by 9 percent. A physical culprit, it seemed, had been identified.

A local mathematics professor named Jason Wilson monitored this fallout with great interest. A phenomenon that seemed far removed from the Biola University baseball fields was actually right up his alley.

Wilson’s fascination with baseball was piqued in 2010. One of his students, Jarvis Greiner, was a pitcher on Biola’s baseball team. Using his own teammates as research subjects, Greiner tried to quantify the quality of a curveball for a class project. His methodology was crude: using three low-grade cameras and a tape measure, Greiner assigned a score on a scale of 0 to 100 to “grade” each curveball on how difficult it would be for a batter to hit.

The project was a home run in class. Wilson then set out to apply the same rubric to grade major league pitches. MLB already had Pitch F/X cameras in each stadium at the time, which tracked the trajectory of every pitch thrown in every game. As it turned out, big league curveballs were easier to “grade” than anything thrown on a back field at Biola.

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In 2014, the results of Wilson and Greiner’s study were published in Chance magazine, a journal of the American Statistical Association. The “Quality of Pitch” database was born. Ranking every pitch in baseball by its granular components – horizontal break, vertical break, lateness of break – had never been easier in the public sphere.

Flash forward to 2018. In light of the revelations about the changing physical properties of baseballs, Wilson had a new project on his hands.

“The two theories everybody was talking about were one, the juiced ball theory and two, the uppercut swing,” Wilson said in a telephone interview. “Well, what about the pitch? If you change the pitching, obviously that’s going to have an effect on home runs as well. In the past, we observed a weak but real correlation between quality of pitch and home runs. That’s the reason we went into it and suggested that we should find something.”

To the extent that the pitching part of this equation garnered much notice, it usually came in spurts. An uptick in blister injuries in 2016 and 2017 furthered the notion that the physical composition of baseballs was affecting pitchers in new, unwanted ways. During the 2017 World Series, pitchers and coaches for the Dodgers and Astros openly questioned the “slickness” of the baseballs; the startling report in Sports Illustrated suggested pitchers who threw sliders would be affected the most.

Wilson’s research suggests that pitchers – fastball pitchers in particular – might have been hindered by a change in the baseballs even more than previously believed.

Comparing every pitch thrown in 2016 and 2017, including the postseason, Wilson concluded the league-average pitch quality dropped across several major pitch types: 11 percent for four-seam fastballs, 2 percent for sinkers, 4 percent for cutters and 3 percent for sliders.

The likelihood of this outcome defied mere chance.

Year-to-year quality of pitch “certainly fluctuates,” Wilson said. “What stands out is that that one was across the board. Every single category, you’ve got a drop.”

Looking at the individual components of pitch quality, Wilson said that vertical break was “the strongest component that was related to the decrease in quality of pitch and the increase in home runs.” At the same time that home runs were increasing, at the same time that the laces on major league baseballs were wider, pitches were breaking less – with little regard for who was throwing the pitch, and what kind of pitch was being thrown.

From the time he first battled a blister after the 2015 All-Star break, Dodgers pitcher Rich Hill has been outspoken about the changing physical properties of baseballs. I asked him Wednesday for his personal take on Wilson’s research. Would the observed change in the laces affect a pitcher’s ability to produce vertical movement?

“Definitely,” Hill said. “Take a cue ball, no seams. In theory, you could make that ball curve. You could make that ball have vertical drop. The problem is that you’d probably have to put a lot more pressure on that ball to make that movement happen than you would with a ball that had some sort of seams. Take that sphere, and change it to something with a little seams, then something with more of an exacerbated seam – changing the height and width of the seam –  you’re going to change the horizontal and vertical movement of the ball.

“There’s no doubt in my mind that changed the movement of the ball out of the pitcher’s hand those years.”

Hill is only one pitcher, so I ran the same questions by Rick Knapp, a veteran pitching coach currently with the Durham Bulls, the Tampa Bay Rays’ Triple-A affiliate.

Knapp said that, from his experience, pitchers typically struggle with grip when they move from Triple-A to the major leagues. The smoothness of the ball, and the height of the laces differ widely. This difference is the exact reason why Triple-A balls will be made to major league specifications for 2019.

By Knapp’s reasoning, the pitchers who were already experts at getting more vertical movement out of their pitches before 2016 and 2017 would demonstrate improvement in this skill, while other pitchers – specifically, those who rely more on velocity – would suffer.

“Take Marco Estrada,” Knapp told me. “Look at his fastball vertical movement.”

OK.

The Quality of Pitch website doesn’t allow for pitch component analysis within the same season, so I compared Estrada’s QOP data in 2014 and 2016. Sure enough, Estrada ranked in the 80th percentile of four-seam fastball movement in 2014, and the 86th percentile in 2016. In 2017, he jumped to the 87th percentile. In 2018 – a season in which home runs decreased, and fewer pitchers (including Hill) observed differences in the composition of baseballs – Estrada fell back to the 81st percentile.

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The data observed exactly what Knapp predicted.

Wilson’s study attempted to quantify how, and how much, pitch quality suffered for the change in baseballs after the 2015 All-Star break. He didn’t zero in on why some pitchers may have succeeded because of the changes to the baseball, but perhaps Estrada and others were better off as a result.

Wilson concedes there’s plenty of room for future research. For now, the amount of agreement is telling: The pitching coach, and the pitcher, and the statistician all agree there’s a story to be found in the data.

“If that ball is different? These guys are pros, that is their craft,” Wilson said. “Change a piece of that, and that affects everything.”

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