The pitchers whose spin rates fell most after a crackdown on sticky substances

By Josh Katz, Kevin Quealy and Tyler Kepner

Baseballs aren’t spinning the way they used to.

More than a month into Major League Baseball’s increased scrutiny on the application of prohibited sticky substances to the ball, spin rates on fastballs have fallen about 4%, as strikeouts have decreased and on-base percentage has risen — midseason changes without parallel in decades.

The drop began around June 3, when Major League Baseball made it known that it would address the issue. It began to level off around June 15, the date MLB announced enhanced enforcement procedures, including in-game inspections by umpires and the threat of 10-game suspensions for pitchers found violating the rules.

Increased spin rate can add movement to breaking pitches. With fastballs, it lets the pitch stay elevated longer, making it appear the ball is rising.

Although applying any foreign substance to a baseball has been prohibited since the 1920s, use of sticky substances like Spider Tack (an adhesive created to help people hold on to the enormous Atlas stones hoisted in strength competitions) was an open secret.

This spring, hits were near record lows. Strikeouts were at record highs. Pitchers were so dominant that by mid-May they had racked up more than a typical season’s worth of no-hitters.

And spin was at the center of it. The changes in spin rates — measured using data from high-speed cameras that track every pitch of every game — are the clearest evidence that substances like Spider Tack were a significant factor in the dominance of pitching. These allowed pitchers to grip the ball so well that they could generate more torque on pitches, which in turn allowed them to spin the ball faster, making it harder to hit.

What’s changed

Typically, walks become less common as the season progresses. In 2021, walks increased after June 15 for the first time in decades, and the share of at-bats ending in strikeouts dropped to 23%. These contributed to the biggest increase in on-base percentage since at least 1990.

To measure the crackdown’s effect, The New York Times examined data from every fastball from 2017 to 2021, about 1.7 million pitches, and compared spin rates in previous seasons with the rates in 2021.

In a typical season, a pitcher’s spin rate doesn’t change much: The rate on a fastball in May is usually close to the one on his fastball in September. But this season, when even old-fashioned concoctions like rosin (legal) and sunscreen (illegal) faced scrutiny, most pitchers’ spin rates decreased after June 3. Of the 131 pitchers in our data set — those who had thrown at least 150 fastballs since June 15 — fastball spin rates fell for all but 29 of them. A handful of pitchers’ spin rates changed drastically.

Rob Manfred, baseball’s commissioner, focused on the positive effects on the game’s offense, calling the changes “very promising.” He was particularly pleased there had been no increases in batters hit by pitches — a point that he has made before and that has been backed by data showing batters have been less safe in this recent era of sticky substances.

“Those are all huge positives for us,” Manfred said.

A 200 RPM difference

A fastball going to 2,400 revolutions per minute from 2,600 might not seem like much. But that additional spin can account for an extra inch of movement on a fastball — and significantly more for some pitchers — said Michael Fisher, founder of Codify, a company that provides customized analytics to dozens of major league pitchers. That can mean the difference between a three-run homer and an inning-ending double play.

Further, the extra spin can confound hitters who have built up a lifetime of what Don Teig, a consultant who has worked with major league teams on the role that vision plays in maximizing motor performance, calls “visual memories.” Those are ideas about what different kinds of pitches look like in the fraction of a second a batter has to make a decision.

That extra movement from sticky substances can render those memories useless.

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