MASTER NOTES: Bauer Notes (This article is A$$)

Do you know what a “Bauer unit” is? I’ll give you a hint: It has to do with pitchers’ “Spin Rates,” the amount of spin they impart when they throw the baseball.

Give up?

Bauer Units are the name given to a metric that divided a pitch’s spin rate by its velocity. The metric was invented by Driveline Baseball, the Seattle performance lab that runs an excellent website about pitcher mechanics. The Bauer unit is named in honor of Cleveland starter Trevor Bauer, who is a very interesting guy, a mechanical engineering major (subscription required) who builds his own drones and control systems, and also applies his interests to pitching, and who contributes videos to the Driveline site. You really should check out his work. It's interesting.

Bauer has quite a keen interest in spin rate. He owns one of the machines used to track spin rate, as well as high-speed video cameras and other advanced equipment to help him analyze his own mechanics and to theorize about mechanics in general. And in his experimentation, he has convinced himself (and me, for what it’s worth) that increasing the stickiness of the fingers-to-ball interface (me, trying to sound all engineer-like), whether with pine tar, or a blend of melted-down Firm Grip and Coca-Cola, increases the spin rate.

Recently, there’s been a bit of a Twitter feud going on between Bauer and the Houston Astros. In case you missed the news, being occupied with more important things, like ... well, anything, tweeted on Tuesday an observation:

“If only there was just a really quick way to increase spin rate. Like what if you could trade for a player knowing that you could bump his spin rate a couple hundred rpm overnight...imagine the steals you could get on the trade market! If only that existed...”

The media inferred that Bauer was talking about the Astros, who got a steal on the trade market by acquiring SP Gerrit Cole in the offseason. Cole has started the year as one of the best starters in baseball, with a 1.73 ERA in six starts and a strikeout percentage of 39.6% of batters faced, the highest rate for any starter in the league except teammate Collin McHugh, who is right at 40%. Cole’s previous season high was 24%.

Cole’s performance has fueled rumors are that the Astros are teaching their pitchers how to use pine tar to increase their grip on the ball. A better grip means the pitcher can impart more spin, and thus get more movement.

Now you’ll note that Bauer did not mention the Houston Astros in his tweet. Nonetheless, several Astros fired back, putting me in mind of this sort of conversation:

Mom: Somebody ate four cookies.

Kid: It wasn’t me. And besides, I was hungry.

One of those responses came from Lance McCullers, who tweeted: “Jealousy isn’t a good look on you my man. You have great stuff and have worked hard for it, like the rest of us, no need for this. I will ask though because my spin rate and spin axis on my 4 seem (sic) is a$$.”

Before I go on: Is “ass” now a complimentary thing to say about something? When I was Lance McCullers’ age, which admittedly is when Human League and Soft Cell were the future of music, saying to a guy, “Hey, your car is ass” would likely get you a punch in the nose, or at the very least a snide reply that your own ride, a rusty 12-year-old Datsun 510, was not exactly a Maserati either.

Also, it’s pretty interesting that McCullers is so aware of his spin rate (and his spin axis), which indicates how much these super-advanced stats are penetrating the often closed culture of baseball.

Anyway, Cole’s spin rate is indeed up this year. Statcast data at show his four-seam fastball spin is up by about 200 RPM, which is 9%, and his curve spin rate is up by about 4%. Experts say the grip benefit of added spin is most pronounced on four-seamers and curves.

Cole is seeing some benefit in the movement of his four-seamer and the curve. Cole’s player card at says the four-seam has a little more of what the experts call “ride”—increased backspin means it sinks less than hitters expect as it approaches the plate. The result is more swing-and-miss and more flyballs. Cole's curve is breaking more sharply down-and-in to LHH, with about two-and-a-half inches more vertical drop and about half-an-inch more horizontal movement. And while the slider spin rate is up only 3%, he's getting an inch-and-half more horizontal movement.

Perhaps not coincidentally, Cole has changed his pitch mix. He’s throwing a lot more curves and sliders, especially to LHH, and a lot fewer changeups.

For the record, HOU starter Justin Verlander has also shown higher spin rates, though the increase was so small as to seem insignificant.

There are some alternative explanations for Cole’s extraordinary success thus far. Collin McHugh suggested “coaching,” although most web sites devoted to spin rate say it can’t be coached. That said, the Driveline site has a piece explaining that spin rate can be affected by the grip itself— a change in finger position can cause change in spin, but the change in their experiment was always to reduce the spin rate relative to the standard four-seam grip. Several observers have suggested that the HOU front office, whose smarts are so advanced that another team hacked their computers, is deliberately selecting for spin rate, and identified Cole as a target in the belief they could enhance his.

But how to enhance spin rate is the question of the moment. It is possible that pine tar is involved. It seems an open secret that a lot of pitchers use the stuff all the time, that umpires know they’re doing it and basically turn the blind eye (some of the umps have several such eyes to choose from), and that MLB itself also knows they’re doing it and likewise ignores it, even when a baseball finds itself stuck onto Yadier Molina’s chest protector (catchers also put the goo on the ball to help the pitchers). You’ve probably seen the highlight clip of Molina standing sheepishly with the ball welded to his stomach. (If you watch games on, you’ve probably seen it 1,826 times. This week.)

One of the first thoughts that struck me was that increasing the friction between fingers and ball could cause an increase in blisters (Aaron Sanchez’ spin rate this year, when he’s not having blister trouble, is down about 5% from last year, when he famously was).

Bauer has said sticky substances of any kind should simply be allowed, in part because of the safety issue. Improved grip on the ball gives the pitcher a little better control, especially in colder weather like we have seen so much this year. As well, the baseballs themselves this year are reportedly a little harder to grip, and MLB has asked ball supplier Rawlings to find a way to increase the tackiness of the leather.

In the end, the short explanation of the spin rate issue is that it’s still hard to say. Despite all the effort expended to get into the details, the phenomenon is still poorly understood. I expect that further study, especially with super-slow-motion video, might reveal some of the answers. I can't wait.

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  For more information about the terms used in this article, see our Glossary Primer.