Stick(y) in the Mud: Assessing Impact of MLB’s Ban Will Be Difficult

On Monday, MLB umpires began (re-)enforcing Rule 3.02, the clause that bans pitchers from applying foreign substances to the baseball. While we didn’t have any ejections, umpires conducted plenty of searches and managed to do so without needlessly delaying games. Much digital ink has been spilled on this topic since MLB announced the crackdown; just last week, Ben, Jay, and I all weighed in, and comments from the players themselves have run the gamut from measured and reasonable to wildly implausible.

As we enter this new period, the obvious and immediate impulse is to try to measure the impact the rule change is having on the game. We know the teams will: Clubs have paid good coin for elite spin in recent years, and you can bet they’ll be paying close attention to who does and doesn’t lose RPMs as trade season approaches. Fans and writers will surely do the same. Whether assessing league statistics or individual performances, the temptation to compare spin rates against performance will be very powerful in the coming days.

That’s a fair approach. Even before the crackdown, we saw a few peculiar pitching lines. It’s newsworthy that both Gerrit Cole’s spin rates and strikeout totals dropped in recent starts, particularly given his cringey answer to a reporter’s question about sticky stuff two weeks ago. Ditto with Trevor Bauer, who rode a massive increase in spin rate to a Cy Young award and $102 million contract.

Looking at macro trends, there’s plenty worth chewing on as well. Baseball Prospectus’ Jonathan Judge found that the average spin-velocity ratio on fastballs has declined dramatically in June. Even more interesting than that, Rob Arthur showed that fly balls are carrying further than we’d expect in recent weeks, even after adjusting for weather, and that the crackdown looks like a contributing factor: “Sticky stuff may suppress fly ball distance by remaining on the ball after contact. If it’s sufficiently hard or viscous, clumps, beads, or strings of Spider Tack, glue or what have you could effectively increase the surface area of the ball, slowing it down more in flight.”

These are exciting discoveries, but this is also a period of high uncertainty, and one where it will be tempting to draw conclusions from limited data. I’ve already seen firsthand how easy it is to make a mistake while doing so. In his start last saturday, Alek Manoah’s spin rate and horizontal movement were down relative to his previous outings. Some loudmouth shared that observation on Twitter while making a not-so-subtle inference:

In my rush to tweet, I glossed over the nuance (first time that’s ever happened on Twitter, by the way). In the first inning, Manoah’s sliders were averaging 270 fewer RPMs than usual, which drew immediate attention. By game’s end though, that discrepancy had narrowed down to less than 100 RPM per pitch. As it turned out, his first-inning sliders weren’t suspicious on their own but were artificially low because of a classification problem. In his fifth pitch of the game, he tossed a change that Statcast incorrectly identified as a slider:

This is not the first time this season that Statcast misdiagnosed one of his changeups as a slider. It’s a good reminder that nothing is perfect and that this incredibly useful and impressive tool is not immune to the occasional boo-boo. In any case, the four pitches that were actually sliders that inning looked normal. The one he threw to fan Trey Mancini actually had more spin and a higher break than his average bender:

Even before accounting for the impact of these incorrect classifications, Manoah’s spin rates weren’t out of the ordinary. In fact, his fastball had a higher spin-velocity ratio than his yearly average. Whether or not Manoah was doing anything different than normal on Saturday, we can’t tell just from the Statcast data.

Moreover, the connection between performance and spin fluctuation is not always clear. As one example, Arthur noted that Cole’s fly balls started carrying further once his spin rate declined, but that the opposite had happened to Bauer. A variety of variables will also make it hard to discern what’s going on. Take sunscreen, for instance — the agent of choice for many pitchers. The league’s decision to ban it at night and in domes raises plenty of fresh questions. At what point is it so dark out that that a pitcher can’t wear sunscreen? Do pitchers have an obligation to avoid applying sunscreen to the ball, even on a hot afternoon? These issues and more preclude a simple interpretation of impending events, particularly among individual hurlers.

Enforcement is another significant variable. Will umps really eject people all year for wearing too much Banana Boat? Or will a short-term crackdown eventually yield to a policy more lenient of grip-enhancers like sunscreen? There’s also a chance that this winds up becoming totally inconsequential and that the league loses interest after a bit of high-profile scapegoating.

This isn’t to say that an absence of sticky stuff isn’t having any effect. Some of the signs will prove obvious enough. The changes in spin-velocity ratio can’t be explained away by variance, for instance, and it’s hard to imagine that the guys who are losing hundreds of RPMs on their stuff won’t suffer at least a little bit. And if we see home runs surge back to 2019 levels over the summer, we’ll have a pretty good idea what caused the spike.

Whatever the long-term effects of this policy though, we’re not going to know all of them right away. I wish I had a more sophisticated observation to conclude with here. Perhaps we should pretend it’s April 2 and apply the usual small sample caveats as we try to suss out the effects of this development. More likely, now that you have finished this article, you can join me at Statcast for another round of spin derby.





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dozingoffdad
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dozingoffdad

You see, it would be this mat that you would put on the floor….

Psychic... Powerless...
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Psychic... Powerless...

Yes, FYI, subhead says, “…use your jump to conclusions mat cautiously”