Disclaimer: If we wanted to, this article could be ten pages long and still cover only a fraction of the importance and complexity of Spin Rates in Baseball. This is meant as a brief overview and discussion on this most meaningful of statistics, but is not a definitive guide. Hopefully this sparks your interest to read up on some of the fascinating new literature on the subject. This is a compilation of knowledge gleaned by some seriously ingenious folks, please patronize their sites, click the links, and subscribe to their various sites and pages. There is much still to do and much to debate, feel free to do so in the comments.

The Statcast Era is upon us, and it features a literal treasure trove of new data and perspectives that are still being torn over and argued about among baseball fans, both amateur and professional alike.

But one stat that is starting to take exceptional importance is that of Spin Rate, which measures the rate at which baseballs spin as they approach the plate. Before Statcast had been introduced to us unwashed baseball watching barbarians, it was easy to wonder why someone like Koji Uehara could do this

This pitch was a blazing 88 mph. At the top of the zone. At the top of the zone and middle-ish in. And the hitter was late, and couldn't square the ball. Why?

Well, even though the pitch was only 88mph, it was spun in at over 2400rpm when the MLB average fastball usually sat at 2200rpm. While it seems trivial, that extra 200rpm is the difference between a swinging strike and an absolutely smoked baseball.

Now, every pitch operates differently. Curve balls have top spin, Fastballs have backspin, and sliders do a million different things because sliders are thrown a million different ways and I can't be bothered to research it further because that road is the road to madness. What is curious is that spin rate means drastically different things for different pitches. High spin rate can be both good and bad, low spin rate can be both good and bad, it all depends on the pitch and the pitcher in question.

To emphasis this point, gaze upon the pitch that lost the WS in 2015, a splitter that had too much spin thrown by then lock-down closer Jeuri, Jeremy, Juery, Mr. Familia of the Mets.

Familia getting wrecked via statcast. Its valuable, click the link.

Take a look at the difference that an extra 100rpm can mean.

His splitter/sinker had too much spin, so it didn't sink. It sat right in the middle of Gordon's murder zone, and he tied the first game of the 2015 World Series, setting the stage for the Royal's eventual victory and the Met's eventual doom. As we can clearly see, spin rates are essential depending on the pitch.

Before we start diving into what spin rate means for different pitches, its important to understand what Spin Rate is, and how it is defined. So lets jump right in.

Spin Rate Defined

Spin Rate, via the MLB Glossary is defined as thus:

A pitcher's Spin Rate represents the rate of spin on a baseball after it is released. It is measured in revolutions per minute. The amount of spin on a pitch changes its trajectory. The same pitch thrown at the same Velocity will end up in a different place depending on how much it spins.

Seems pretty self explanatory. But not all spin is equal. As baseball prospectus writer Alan M. Nathan explains

The reason has to do with the vector nature of the spin: It has a magnitude and a direction...and can be represented with Spin Vector (W), Gyro-spin (W2), and transverse spin (Wt)

This is a meaty and hard to understand concept, but in its simplest form (Alan is a mathematical savant and the defacto expert at this area of analysis, I attempted to get ahold of him but failed) is that not all spin is equal, that transverse spin is valuable to fastballs, higher spin rates mean more lateral movement and lower spin means more vertical movement. And that at a certain point higher spin rates for curve balls and breaking pitches become dramatically less impactful for their total movement. Alan explains that at a certain point even doubling the spin on a curve ball will have a negligible effect at a certain point. Gyrospin which is often present is like the spin of a bullet, and its impact is either negligible or a total non issue, although this isn't entirely clear.

Simply Put: For fastballs, more spin or much less spin = more movement. When combined with higher velocity, fastballs are often even more effective with more spin. This concept is illustrated in the mathematical formula called "Bauer Units".

A Bauer Unit is derived from Spin Rate (RPM) / Velocity (MPH). Normalized, the average pitcher has a Bauer Unit of 24, with more velocity or spin increasing the Bauer unit. The idea comes from the masters at Driveline Baseball, who go in depth about it here. The basic premise is, the higher the Bauer Unit, the more effective the pitch. It is a valuable read and goes into depth on how more velocity can be less effective than a fastball with higher movement. To put that into perspective, hard throwing Ken Giles has a lower Bauer Unit fastball than Marco Estrada, who rarely exceeds 90 MPH.

Spin rate also operates within the confines of the Magnus effect, which I have touched on briefly before, is simply the effect of spin on how much a pitch resists the effect of gravity. To quote my last fanpost,

Fastballs also work within the effects of Magnus backspin. Backspin on a fastball creates lift force. Without going too heavy into the science, the more spin on a fastball, the longer it takes for it to drop. So, for a sinker to sink, or a fastball to be heavy, it needs to be thrown with less spin than a normal fastball.

Curve balls are the same to a certain point. But what Alan notes and explains here is that spin rate is still a science in progress, and the data is still not perfect.

Additionally, a pitchers delivery affects the ball as well. A pitchers release, extension, and grip will all effect the patch and spin of the ball as well.

With a rudimentary understanding of the different types of spin and their effects on a baseball as well as the magnus effect briefly explained, we can dive a bit more into what spin rates mean for each individual pitch

Fastball Spin

Fastballs are the meat of all pitches being thrown on any given day on any given baseball field, even though that trend is changing, as demonstrated in this chart:

Fastballs rely on backspin. As discussed, fastballs with higher spin than the MLB average of 2,263.15 seem to "rise", as in they stay up higher than the aforementioned average spin fastballs. Higher spin fastballs tend to be more effective at getting swinging strikes, as illustrated through this mind numbing excel sheet, with the data points representing swinging strikes.

The chart clearly illustrates a trend that more velocity + spin = swinging strikes, with a few curious outriders.

Here is an illustration of a 92mph fastball thrown with 2400 rpm, 2200 rpm, and 1800 rpm.

That may not seem like a big deal, but at 2400 rpm and at 1800 rpm, there is more than enough movement to avoid the barrel of a bat, getting either a pop up, strike, or ground ball.

So what does this mean in real world effects? Well, here is the batting averages of these different spin fastballs (in 2016)

1. Below 2100 RPM- .304 MLB average
2. 2100 to 2600 RPM- .267 MLB average
3. Above 2600 RPM- .197 MLB average

Curveball Spin

Curve balls, unlike fastballs, relying on top spin. Curve balls today are not your grandpas big loopy silly bugs bunny slow hooks. They are getting thrown harder and harder, and more often now than they've been in many years. This was best typified by Lance McCullers (who will show up again shortly) throwing 24 straight curve balls to Yankees hitters, completely dominating them.

Click the link, its a gorgeous display.

That was a ridiculous, ballsy display of confidence in his curve, one that was well deserved. Going off what we've already learned, we can see that more spin should mean more movement, and this generally holds true for curve balls.

First, there are many different variations of the curve, straight, power, knuckle, 12-6, 11-5, etc etc etc. As a rule, they tend to be thrown pretty similarly and each individual pitcher has their own unique way of throwing them. But they all tend to be more successful the higher the spin rate. I'm lumping them all together and if you think that is a bit of a generalization.... well you're right but hell I'm doing this for free and this took awhile to do and you'll need to cope. Moving on.

Curve balls, as MLB.com explained, have a remarkable and almost comical range of Spin. They range from under 1000 rpms to over 3000 rpms. Curve balls with RPMs between 1000 and 1750 result in fewer swinging strikes and less ground balls, averaging about 40% ground balls. Those above 1750 rpm tend to exceed a 50% ground ball rate.

Curve balls have the most "useful" spin, as discussed in the first section of this article, of any pitch. Nearly 75% of curve ball spin is "useful". This means that as a rule, the higher the spin rate the better movement the pitch gets.

However, it can be noted that their is a definitive difference in success rates between horizontal curves and vertival curves. Horizontal curves strike out more batters, but result in more hard contact, while vertical curves have a much higher ground ball rate but lower strike out totals, as explained more in depth here.

Lets take a look at some curve balls, namely several pitchers that have heavily relied on them now or in the past.

Garrett Richards- 3000+ RPM Curve Ball

Garrett Richards has a devastating Curve. It gets incredible movement due to its intense RPM. Its also thrown between 79MPH to 82MPH. In terms of RPM, Garrett has an elite curve ball.

Craig Kimbrel- 2.499+ RPM Knuckle Curve Ball

Craig throws his Knuckle Curve anywhere from 85 MPH to 90 MPH. Its a devastating pitch that gets exceptional two plane movement.

Clayton Kershaw- 2350+ RPM Curve Ball

Clayton's curve is legendary. Remarkably, in terms of pure spin, its unremarkable. However, it averages nearly 9 inches of vertical drop and its thrown at a spin rate similar to his fastball, so it often freezes batters in their place.

Drew Pomeranz- 2100+ RPM Curve Ball

Drew Pomeranz's curve has made him a force to be reckoned with. At one point, he had thrown 2000 curveballs while only allowing 5 home runs off the pitch. Its a beauty.

In summation, more spin means a more effective curve ball. However it also depends on the break of the pitch and they type of curve that is thrown. A sweeping, high spin rate curve will get more swings, but some of those will be harder hit than those of a more vertical curve ball.

Now that we've looked at Fastballs and curve balls, we can take a quick stab at change-ups and their derivatives.

Change-Ups

As I discussed in a piece I wrote ages ago, change-ups are a wonderful tool. Unlike fastballs and curve balls however, they are often thrown intentionally to have less spin and speed in order to deceive a hitter. Some pitchers have had success with higher RPM change-ups, but as a whole they are thrown with much less spin than the average MLB fastball.

The league average in 2017 was hovering around 1700 RPM for change-ups. There is no definitive data I've seen that 100% indicates whether more or less spin will make a change-up more efficient, made more difficult by the mind numbing semantics that goes into classifying pitches and the fact that Statcast often misidentifies change-ups that mean the data is kind of .... meh.

But regardless, lets take a brief look at some change-ups and draw our own conclusions.

Felix Hernandez- 1750+ RPM Change-UP

Felix's change up is legendary, and its at the higher end of RPM and of velocity. Some pitchers like Felix and Greinke throw their changes at very similar velocities to their fastballs, which is becoming more popular but historically not prevalent. Most change-ups have 7-10 MPH separation between the fastball and the change-up, going off the idea that a change-up is supposed to get a hitter to think its a fastball, and swing over and early.

But Felix made it work.

Nathan Eovaldi- 950 RPM Splitter

Nathan Eovaldi was a tragic tail of immense velocity but no deception. He could throw in excess of 100 MPH, but was routinely smacked about like a poorly mannered child. His splitter here is used to show the opposite side of the side of the RPM spectrum.

In summation, more spin isn't ideal for a change-up, but its not necessarily a deal breaker, it depends on the pitch and the pitcher who throws it.

Last and by far least, the "slider"

Sliders and all their Nonsense Derivatives

Sliders are bull-$@#&. There is so much hybridization and variations and semantic arguments on classification that it literally tears my brain asunder trying to summarize and explain all said variations.

So I'm not going to do so. Here is a link where Brandon does a stellar job on the subject. Read, then comeback. I'll wait.

Alright, sliders are so different that it is IMPOSSIBLE to definitely say whether or not that higher or lower spin rate is good or bad. More spin does hold true that it generally means more movement, but even that isn't absolutely true. Lets take a look at a few outliers so you know why its so confusing.

MLB does a small blurb about it here.

Darren O'Day- 1800-2200+ RPM Slider

Darren O'Day's slider seems to be all over the place. Sometimes its a lot slower and more dramatic, but this year he's higher spin slider seems to be the norm. Its wibbly wobbly, and its pretty standard.

Chaz Roe- 2880+ RPM Slider

This is on my short list of the best pitch ever thrown. That thing, THING, is a monster. A horrific all consuming monster that has been brought by the devil through his tool Chaz Roe to make hitters suffer.

I love this gif.

Regardless, its thrown at 2800 RPM, has outrageous two plane movement and it breaks towards the hitter, then away, then down. Its inhuman. The spin rate clearly plays a decisive role in its movement, as it acts almost like a sweeping curve than a slider.

Chris Sale- 2450+ RPM Slider

Chris Sale's slider is arguably the most monsterous in the MLB. He gets incredible movement on it, and he can bury the thing anywhere he wants.

Ask Torii Hunter

He swung at a pitch that hit his back foot. Ouch.

So in summation, Sliders are hard to qualify, but they seem to act on the same principal that more spin equals more movement and more swinging strikes.

Overall

Spin rate is one of the newer and more prominent statistical tools. As the science expands and becomes more mainstream, we can hope that more tools and perhaps more ways to better utilize spin rate will come along for both professionals and amateur fans like myself.

As always, Go Tigers!

Editor's note: If you enjoyed this article, check out a couple more JajaBojangles' posts on the fastball and the changeup.