When MLB announced that it was cracking down on pitchers’ use of foreign substances on Tuesday it was unclear precisely what effect it would have on the game.
Spin rates have dropped around the league in recent days — and hitters numbers’ have improved — but as Ben Lindbergh pointed out at The Ringer, offence tends to take off at this time of year with rising temperatures, and it’s hard to pin down the exact effect.
This change in rule enforcement will also affect pitchers asymmetrically. Some subset of them will adjust to the new landscape relatively well while others struggle — like Tyler Glasnow, who attributes a lack of sticky stuff to his most recent injury.
For now, there’s a great deal we don’t know, but there are a few educated guesses to make — especially when it comes to the other side of the equation. It’s safe to say spin rates are going to come down around the league. That means hitters who tend to struggle with high-spin pitchers will be put in a better position to succeed.
On the Toronto Blue Jays, that means there are a few batters who should be thankful to see the rules change. The pitches where high spin rates are most correlated with success are four-seam fastballs and breaking balls, so a quick examination of which Blue Jays struggle with four-seamers, sliders and curveballs with the highest spin rates should give us a sense of who will benefit most from the new offensive climate.
In order to pin down which Blue Jays struggle the most with high-spin fastballs, I looked at how the team’s regulars (Vladimir Guerrero Jr., Bo Bichette, Marcus Semien, Teoscar Hernandez, Randal Grichuk, Cavan Biggio and Lourdes Gurriel Jr. — plus George Springer) have fared against four-seamers with spin rates in the 80th percentile and above, as of MLB’s announcement.
That means heaters with a spin rate 2429 or better, approximately the spin generated by Lucas Giolito. Below is a chart of how they’ve fared on such pitches since the beginning of the 2019 season by batting average, slugging and called strikes+whiffs:
While Hernandez has had some difficulty making contact with the high-spin four-seamer, it’s clear that Gurriel Jr. and Biggio stand to be the major beneficiaries of new rule enforcement.
The issue is a little bit complicated, though, because spin rate is highly correlated with velocity, so it’s not 100 per cent clear if Gurriel Jr. and Biggio struggle with high spin or simply fastballs with serious juice. In order to tease that out, I looked at how they performed against heaters 95 mph+ with a spin rate below 2429:
Neither player excels against velocity with less spin, but their numbers are significantly better. That means we should see fewer instances of Biggio being blown away by pitches like this 2515 RPM heater at 93.7 mph:
… or Gurriel swinging through this 2465 RPM fastball from Dylan Bundy travelling at a modest 91.1 mph.
Sliders are less commonly associated with spin rates than curves, but they are significantly more common — and can run RPMs as high as Trevor Bauer's 3001 on the way to confounding hitters. Here’s how the Blue Jays have fared against 80th+ percentile sliders by spin rate (2634 RPMs, or approximately Griffin Cannings’s average), in that same 2019-2021 span.
The numbers here are significantly worse across the board, and they’re actually higher than they’d be on many teams. Guerrero Jr.’s ridiculous 2021 has brought his career wRC+ to an elite 133, and his run value against sliders according to Statcast (+14) is the best in the league this season. His numbers look good whichever way you slice them. Springer was the league’s best slider hitter in 2019 by the same measure, which helps explain his numbers. Meanwhile, Gurriel Jr. has had a reputation as an excellent breaking ball hitter for years.
Everyone else looks human because sliders have more movement than fastballs and are more likely to be deployed in pitchers’ counts. Semien, in particular, has struggled, and may see some of those struggles alleviated in the weeks to come.
That could mean fewer awkward swings like this one:
Curveballs result in the highest spin rates of any pitches, but stats against them are a little tougher to feel confident about because the sample sizes are small and they’re rarely thrown in the strike zone — making it tough to get hits, particularly extra-base knocks, against them.
With that in mind, here’s how the Blue Jays have fared against 80th+ percentile curves by spin rate (2725 RPMs, or approximately Jacob deGrom’s average):
Biggio pops off the screen once again, as does Grichuk, who similarly hasn’t gotten an extra-base hit off a high-spin curve in the last three seasons. Hernandez deserves a little credit for his success against the pitches, which includes a pair of home runs, and for the first time Guerrero Jr. looks like less of a world beater.
These numbers don’t tell us anything definitive, especially considering we’re headed into uncharted waters over the next couple of weeks. If nothing else, though, it seems like Biggio might get a little more comfortable at the plate — not that that’s been an issue lately.