Foreign substance enforcement brings lower spin rates, improving offense

Baseball’s enforcement of foreign substance use by pitchers, doctoring the ball to add velocity and spin rate, began with a bang — or rather, it began with the dropping of drawers on the field.

That’s what Oakland Athletics reliever Sergio Romo did when an umpire stopped to check him for the presence of any sticky stuff June 22. Romo’s incident followed Max Scherzer’s spectacle, finding himself unbuckling his belt in the middle of an inning before an umpire felt the Washington Nationals ace’s sweaty hair for any foreign substances. There were none.

Those incidents added drama to MLB’s decision to ramp up enforcement of foreign substances, which have long been banned but laxly policed until recently. But in the two weeks that have transpired since, the on-field displays have given way to a grudging acceptance of the new norm, with pitchers handing umpires their hat and glove before getting on their way to the dugout — no disrobing necessary.

And while two weeks in baseball is a small sample size compared to the full 162-game slate, the changes have been noticeable, albeit minute in some senses.

The largest difference between pre- and post-enforcement times has been the sharp reduction in spin rate, which is a measure of how many revolutions a baseball makes per minute across the 60 feet, 6 inches between the mound and home plate.

With a decline in spin rate may come an uptick in offense that could already be on display, despite the small sample size. For baseball, those are the early signs of what could be a successful enforcement policy, leveling a playing field that seemed to tip in the pitchers’ favor in recent years.

Over the first two months of the season, that dominance made itself known. Through May 31, the MLB-wide batting average of .236 was a historic low. Batters were slugging at a .394 clip and struck out 24.2% of the time.

Since foreign substance enforcement began June 21, the offensive numbers have improved. The next 15 days of games yielded a .244 batting average and .410 slugging percentage. The strikeout rate dropped to 23%. The home run rate rose from 3.4% to 3.8%. They’re small changes, but perhaps emblematic of a swing back toward neutral.

“The spin rates have gone down, and the offensive numbers have gone up,” said Tim Kurkjian, an ESPN baseball analyst. “Which I think is good for baseball, because I think the pitching was just far too overpowering for the first two full months of this season.”

As the weather gets warmer, the ball carries more. Therefore, making sweeping judgements based on a two-week window is a hard sell. But the steep decline in spin rate can be attributed to the lack of sticky stuff available to pitchers.

According to Baseball Prospectus writer Robert Arthur, the spin-velocity ratio had been steadily climbing since 2018. But in mid-May, the revolutions per minute dropped off the table for many pitchers. Others took longer to show signs of any variation from usual.

The sticky stuff crackdown has produced just an absolutely bonkers reduction in spin rates across the league. We really don’t have a good historical parallel for how low RPM will end up, but this change is going to cut K% and boost runs by a lot. https://t.co/c5ST8JF3t0 pic.twitter.com/k98ASf223q

— Rob Arthur (@No_Little_Plans) June 25, 2021

Scherzer, for instance, saw his spin rate show the first signs of major decline with his start against the San Francisco Giants on June 11. Enforcement hadn’t yet started, but the news of potential enforcement had already spread. In that game, Scherzer’s curveball spun 238 fewer rpm than his yearly average, and his fastball dropped 80 rpm, per Baseball Savant. His next start, when enforcement began and Phillies manager Joe Girardi asked umpires to check Scherzer for a foreign substance midway through an inning, Scherzer’s four-seam spin rate declined 105 rpm. His curveball was down 170 rpm and his slider dropped 155 rpm.

The Yankees’ Gerrit Cole saw his spin rates plummet during his start June 22, with his fastball 215 rpm against the average. His sinker dipped 326 rpm, his slider 205 rpm, his knuckle curve 147 rpm and his changeup another 96 rpm. The Dodgers’ Trevor Bauer saw the same during his June 23 start: his fastball, slider and knuckle curve all lost at least 109 rpm compared to his season average.

Scherzer has maintained his strong performances despite a decline in spin rate. Cole, meanwhile, has allowed 10 runs in his last two starts, with his most recent outing lasting 3 1/3 innings. Those pitchers are part of a larger trend in spin rate declines, and offenses are beginning to heat up.

“It looks like this might be because of lower use of sticky substances,” said Andy Andres, a professor who teaches a course on baseball sabermetrics at Boston University and Tufts University. “In other words, [the offensive numbers are] trending the right way you would expect if the spin rates are going down.”

On June 30, MLB teams erupted to score 204 runs — the most runs scored in a single day since 2009.

“That’s a good sign that pitchers maybe were getting an unfair advantage, and now they’re not,” Kurkjian said. “Some of them. I mean, we can’t prove any of this, but it sure seems that way. And I think that’s healthy for the game, that we’re seeing a little bit more offense.”

This isn’t the first tweak MLB has made to alter batting average. After the “Year of the Pitcher,” in which batters set a record-low .237 average, MLB lowered the height of the mound by five inches in 1969 and shrunk the strike zone.

Cutting down on foreign substance use could be another example of that, aiming to alleviate some of the struggles against pitching that has become increasingly dominant — and perhaps a little sticky — of late.

A larger sample size at the end of the season will glean more information, proving if the slight offensive upticks were more than a coincidence or trick of the weather. But for the time being, the elevation of offensive outputs while spin rates decline are an early indication that the foreign substance enforcement is impacting the game.

“It’s definitely gone down, the spin rates on certain pitches because of the crackdown,” Andres said. “And you’re likely to see better contact from here on out. Less strikeouts, better contact, more barrels, more hard-hit balls, less pop-ups, less grounders — all those things.”