MLB’s “Sticky Stuff” Ban and Which Pitchers it Has Affected the Most
On June 3rd, 2021, MLB commissioner Rob Manfred announced a crackdown on MLB pitchers using foreign substances. Pitchers use substances such as pine tar and Spider Tack, a sticky substance meant for heavy weightlifting, to improve their grip on the ball and increase spin rates. Although these substances were never legal, little was done about their use until this year. Since the “sticky stuff” ban went into effect on June 21st, the average four-seam fastball spin rate has decreased from 2307 to 2227 RPM, a decrease of 80 RPM or about 3.5%. Spin rates initially decreased in early June following Rob Manfred’s announcement of the substance crackdown, and further decreased towards the end of June when it went into effect. The lowest daily average so far was recorded on June 26th, with the average fastball only spinning at 2154 RPM (153 RPM lower than the average pre-crackdown). Below are fastball spin rates from this season so far, broken down by daily averages.
Since the crackdown, nearly 50% of pitchers have experienced a drop of 50 RPM or more in their fastball. Substance use is not the only factor in spin rate, but the strong correlation with the crackdown indicates it was a factor. Pitchers have been affected differently, with some seeing their spin rates drop as much as 400 RPM while others, such as White Sox All-Star and Cy Young candidate Carlos Rodon, have had their spin rates completely unaffected. Below are the top 25 pitchers in the MLB who have seen the greatest decrease in fastball RPM since June 21st, as well as their decrease in RPMs.
Out of the top 25 pitchers who have experienced the largest decrease in fastball spin, five of them are All-Stars (Gerrit Cole, Corbin Burnes, Alex Reyes, Andrew Kittredge and Walker Buehler). Gerrit Cole, in particular, has come under a lot of scrutiny since the sticky stuff ban. Cole has seen his fastball spin rate increase dramatically over the past few years, from 2164 RPM in 2017 to 2517 RPM in 2020. Cole’s fastball spin rate by start decreased suddenly after Manfred’s June 3rd announcement, dropping 146 RPM between his June 9th and June 16thstarts, and his ERA has jumped from 2.31 to 2.68 since the ban. Here’s a start-by-start breakdown of his success since June 16th:
June 16 @ Blue Jays: 8 IP, 2 ER, 4H, 1 BB, 4K, W (3–2)
Cole’s only two blemishes in this game came from solo shots by Semien and Biggio. Despite his decreased spin rate, Cole still threw a great game against Toronto and came out with the win. His K/9 rate of 4.5, however, was significantly below his career average of 10.5.
June 22 vs Royals: 7 IP, 2ER, 3H, 3BB, 6K
A solid outing against one of the weaker offensive teams in the AL saw Cole’s spin rate decrease below 2300, a season low for Cole and his lowest single-game spin rate since 2017. Cole ended up with a no-decision, but still performed well in the Yankees’ 6–5 loss.
June 28 @ Red Sox: 5 IP, 6R (5ER), 2BB, 6K, L
Cole’s most runs allowed in a game this year up to this point, and only one less than his entire April total of 7. Cole allowed three home runs, once again a season high and two higher than his April total.
July 4 vs Mets: 3.1 IP, 4 ER, 3BB, 6K
The Mets have scored the second least runs of any team going into the All-Star break, averaging only 3.74 per game, but Cole struggled heavily and was pulled early. This was Cole’s shortest start of his career since September 12th, 2016, against the Phillies. His spin rate was once again below 2350 after rising above 2400 in his start against the Red Sox.
July 10 @ Astros: 9IP, 3H, 0ER, 2BB, 12K
Cole once again looked like himself despite a spin rate back below 2350 RPM. The Astros struggled to hit him all game, with Cole recording 12 strikeouts, five of which came off of fastballs.
Cole’s start against the Astros capped off a very strong first half entering the All-Star break, however, some regression should be expected in the second half. For his career, Cole’s wOBA against is .366 on fastballs over 2350 RPM and .332 on fastballs under 2350 RPM. Since June 9th, 52% of his fastballs have been under 2350 RPM. However, Cole proved against Houston that if he can still be dominant with a lower spin rate. If he is able to continue to adjust, there’s no reason to believe Cole cannot stay effective during the second half of the season.
Other Pitchers Affected
Although Cole has been targeted with the most criticism regarding using foreign substances, three other all-stars have also seen similar declines in fastball RPM. Each of these charts below shows the average fastball spin by pitcher for 2021 by appearance. Notice the large decline by each pitcher around the June 3rd mark, followed by an even further decline around June 21st. Notably, none of these pitchers have struggled greatly since the foreign substance ban. Buehler and Burnes have both seen their ERAs drop since June 23, despite the decreases in spin rate. Some regression may be expected for the second half of the season, but so far these pitchers have continued to be successful. Note, for Corbin Burnes and Andrew Kittredge, RPMs for their primary pitches (Cutter and Sinker, respectively) are displayed below instead of Four-Seam RPMs.
So far, the sticky substance ban has had a modest but still significant effect on pitcher success. Historically, higher fastball RPM has been correlated with higher velocity and a lower wOBA, as shown in the table below. Thus, it’s not too surprising to see that league-wide, wOBA has increased (.318 to .328) and home run rates have also increased by over 5%.
The foreign substance ban has had its fair share of critics, none more adamant than Ray’s ace Tyler Glasnow. Tyler Glasnow sustained a serious UCL injury in June, which he blamed on the suddenness of the ban. However, this ban has injected a much-needed offensive boost into a season that has been criticized for being all too pitcher-friendly. With wOBA and home run rates rising, teams will score more runs, bringing more fans to the ballpark. Gerrit Cole is proof that pitchers can adjust to the ban, and still be effective by making the proper adjustments without relying on any substances. In the next few months, expect a resurgence of offense until pitchers are able to adjust.
Data for this project was obtained using the Statcast package for Python, available at https://github.com/jldbc/pybaseball.
For business inquiries, please contact me at njbuckley.sports@gmail.com.