Mike Bolsinger’s Breaking Ball(s)

Step one for Mike Bolsinger was throwing a unique curve.

Only eight players in 2014 had a smaller velocity difference between their fastball and curve, and his curve is two ticks faster than the average curve, which led me to highlight him in my JABO piece on what makes great curveballs. That piece helped alert the Dodgers’ front office to his viability as a starter. They acquired him and then turned to him when depth became an issue. That gave him an opportunity.

Step two for Mike Bolsinger was adding a third pitch, of course.

Most interesting about this new pitch for Bolsinger might be that it’s not very different from the other two pitches he throws. He threw a cutter and a curve and now he’s throwing a … slider. Everything breaks towards his glove, and everything averages between 80 and 88 mph. Watch him pitch, and you’ll think he’s throwing the same pitch over and over again. Actually, he might be.

Let’s first make sure it’s a new pitch. Any time you throw a cutter and a slider, the pitch recognition recognition algorithms let out a sigh and a groan before they shudder the engine to life. PITCHf/x itself doesn’t recognize that he’s throwing three pitches right now. Let’s just throw all of Bolsinger’s curves and cutters into one group and map them by velocity and movement. Three distinct clusters would be the Tums for our pitch classifications’ heart burn.

Yes. Three pitches. One goes 87-90, one goes 79-82, and the other goes 77-80, and the movement clearly separates the last two even if velocity doesn’t do a great job.

So Mike Bolsinger does indeed have a new slider. You know what, though? Let’s take a look at them in GIF form anyway. Below, you’ll see cutter, slider, and then curve, in order from left to right, from his last start. You can be forgiven for wondering if the last two are truly different.


Three arms in a row like that doesn’t make for easy close viewing, but maybe you noticed something about his arm slot in the last two? They aren’t quite the same. MLBNetwork picked up on this and made this helpful graphic for us, showing the different slots for his different pitches — 12:30, 1:00, and 1:30.


In the aggregate, there’s six inches of horizontal difference between the release point for his cutter and the slider.

This raises the possibility that Bolsinger is throwing one pitch three different ways. Take a look at the cutter and slider grips that Jake Peavy uses. The line between those two pitches isn’t written in bold. And plenty of pitchers use the same two-fingered grip for curveballs, too, and just emphasize coming over the top in their release.

Given what we know of the effect of arm slots on spin, Bolsinger could be throwing the same breaking ball from three different slots to get slightly different movement on each. Of course, this is a bit of an exaggeration — he has to manipulate the pitch differently on the breaking balls than the cutter, in order to get that kind of movement — and yet the different arm slots mean that each pitch will have different movement by the necessity of physics.

Too bad, though — it’s not one pitch. We actually do know that he uses different grips for each pitch. Thanks to Greg Gifford of STATS, we have this image that shows us the raised finger that indicates a curve ball. So they aren’t really all the same breaking ball thrown from different slots.


These arm slots do differentiate a guy like Bolsinger from a guy like Madison Bumgarner (other than, of course, handedness and velocity). While Bumgarner has a fastball, a cutter, and a curve as his three main pitches, and they aren’t necessarily differentiated by great changes in lateral movement, Bolsinger may suffer from deriving his different movements from different release points.

Imagine a hitter that knows that the slider comes from lower down on the clock dial. If he can remember that in the moment and differentiate the release points, he will, in essence, know what is coming.

Perhaps that means that step three is going to be throwing the curve from the slider release point as well. If you don’t have a deep arsenal, you should probably keep them guessing in other ways.

With a phone full of pictures of pitchers' fingers, strange beers, and his two toddler sons, Eno Sarris can be found at the ballpark or a brewery most days. Read him here, writing about the A's or Giants at The Athletic, or about beer at October. Follow him on Twitter @enosarris if you can handle the sandwiches and inanity.

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- Casey -
8 years ago

This is a fantastic post, Eno. I love Bolsinger and love this article.