The advent of Statcast has introduced a new layer of analysis into the baseball world.

We are now able to measure the intricate movements of the baseball.

Enter Spin Rate.

The hot topic of today’s pitching world, but does more spin equal more movement? Does higher spin rate lead to less contact?

We aim to find the answers to those questions in the third part of our physics of baseball series.

If you missed the first two parts, we suggest you visit those before reading here:

Sabermetric Data Collection

Let’s talk about our thought process in collecting data.

The first step was to identify top 10 (and bottom 10) spin rates for four-seam fastball, two-seam fastball, changeup, curveball, and slider.

We then compared spin rates versus horizontal movement, vertical movement, swinging strike percentage, and contact percentage.

The goal is to see if spin rate will affect the measures above and affect the overall effectiveness of a baseball pitcher.

A note here is that that the direction of movement (up or down and left or right) is ignored. The graphs below show the magnitude of movement.

First, we will dive into four-seam fastballs.

Spin Rate of Four-Seam Fastballs

The primary movement of the four-seam fastball is in the vertical plane, due to backspin, that creates rise (you may recall that from our article about the Magnus Force and the Four-Seam fastball).

To make that easier to understand, a pitch with a positive value of vertical movement has less drop on it than a pitch with a lower value.
4 Seam Fastball Spin Rate vs. Vertical Movement
The green line depicts a trendline between the lower spin rates and high spin rates. If we had more time we would have loved to graph all spin rates for all pitches, but the trend is still pretty relative.

The average four-seam vertical movement (10 highest spin rates) is 10.38 inches.

The average four-seam vertical movement (10 lowest spin rates) is 7.45 inches.

Well, these results are what we expect.

If you read our previous articles on the physics of fastball movement, you will know that a pitch with a high spin rate will appear to rise.

But because of gravity, that is impossible.

Essentially, we know that the four-seam fastball is thrown with backspin which keeps the ball in the air longer rather than a ball with no spin.

That is the perceived “rise”.

The induced backspin acts 100% towards vertical moving, assuming the baseball is thrown with a vertical axis of rotation. We will touch more on this later.

Let’s now jump into the horizontal movement of the four-seam fastball.
4 Seam Fastball Spin Rate vs. Horizontal Movement
The average four-seam horizontal movement (10 highest spin rates) is 4.52 inches.

The average four-seam horizontal movement (10 lowest spin rates) is 6.68 inches.

Hmm…

Why is there more horizontal movement (on average) at lower spin rates, than at higher spin rates?

The first thing you may have noticed is that the data cluster has a much larger range at the low spin rates, compared to the high spin rates. This means there is less reliability of the more volatile data.

Digging, back into our knowledge about the backspin and the magnus force, we know that a ball thrown over the top will have a vertical axis of rotation (and very little horizontal movement, if we ignore wind).

But, we can throw some of that logic out as when a pitcher throws sidearm, such as with Sean Manaea of the Oakland Athletics

Manaea is the uppermost data point with in orange (low spin rates).

What this all means is that Sean Manaea is releasing the ball more sidearm than some other pitchers, and is inducing a side spin.

In essence, this means he may be gripping the baseball like a four-seam fastball, but in-reality he is throwing it an angle that makes it act more like a cut fastball or slider.

Basically, that was a longwinded explanation of saying that spin rates for the four seam fastball cannot be directly rated to horizontal movement, since arm slot pays an integral part.
4 Seam Fastball Spin Rate vs. Swinging Strike%
The average swinging strike percentage against the four-seam fastball is (10 highest spin rates) is 10.86%.

The average swinging strike percentage against the four-seam fastball is (10 lowest spin rates) is 4.4%.

So, let’s take a minute and try to rationalize why this could happen.

By now we know higher spin rate of the four-seam fastball affects vertical movement. Inherently, we can infer that the large magnitude of vertical movement (induced by spin) correlates with less contact.

As Greg Maddux as stated, increased movement is more important than velocity.
4 Seam Fastball Spin Rate vs. Contact%
The average contact percentage against the four-seam fastball is (10 highest spin rates) is 78.17%.

The average contact percentage against the four-seam fastball is (10 lowest spin rates) is 89.75%.

Contact rate follows the same path as swinging strike percentage. The higher the spin rate on the four-seam fastball the lower the contact percentage.

Four Seam Fastball Spin Rate Table Wrap-Up

For those who love tables, let’s group all of our findings.

Four Seam Fastball and Spin Rates

Four Seam Fastball and Spin Rates

Not too shabby.

On average increased spin-rates of the four-seam fastball correlates with better chances of success.

Now, let’s move onward to the next segment of the articles.

However, before we do, we want to outline a few changes to the delivery and organization of the article moving forward.

We touched, in depth, on how each metric of vertical movement, horizontal movement, swinging strike percentage, and contact percentage were analyzed for the four-seam fastball.

To minimize the repetition, moving forward we will only present the wrap-up table per pitch type.

The overall summary table will be provided at the end of the entire article.
We digress.

Spin Rate of Two-Seam Fastballs

The table below depicts average vertical movement, horizontal movement, swinging strike percentage, and contact percentage for each range of spin rates.

Two Seam Fastball and Spin Rates

Two Seam Fastball and Spin Rates

Let’s touch briefly on how the two-seam fastball moves.

If we recall the discussion we had in the following article, the two-seam fastball has top-spin, and moves down and to the side (towards the magnus force).

Therefore…

The average two-seam vertical movement (10 highest spin rates) is 6.38 inches.

The average two-seam vertical movement (10 lowest spin rates) is 5.16 inches.

High spin rate results in more vertical movement, which makes sense given that the primary movement (pronation) correlates directly with top-spin.

The average two-seam horizontal movement (10 highest spin rates) is 7.77 inches.

The average two-seam horizontal movement (10 lowest spin rates) is 8.26 inches.

Doug Fister vs Rick Porcello Release Points

Doug Fister vs Rick Porcello Release Points

So, if lower spin means more horizontal movement, does that violate the logic that higher spin rate is better?

If we examine, Rick Porcello release point (image on right) we see that he releases the two-seam fastball ball (purple) between negative 0.5 and negative 2 horizontally.

However, Doug Fister (image on left) releases the ball between negative 1 and negative 3.

What this means is that Doug Fister as a more sidearm action that creates more side-spin.

This in return means, that Doug Fister has more side-spin than top-spin, that creates more horizontal movement (7.3 inches) than vertical movement (6.2 inches).

On the contrary, Rick Porcello has nearly identical splits around 8 inches for vertical and horizontal movement.

The average swinging strike percentage against the two-seam fastball is (10 highest spin rates) is 5.62%.

The average swinging strike percentage against the two-seam fastball is (10 lowest spin rates) is 5.03%.

The average contact percentage against the two-seam fastball is (10 highest spin rates) is 88.13%.

The average contact percentage against the two-seam fastball is (10 lowest spin rates) is 88.97%.

Although the differences are relatively negligible, we need to remember that if each pitcher on average throws 300 four-seam fastballs per year (10 pitchers per group), a 1% difference correlates with 30 additional strikes.

Let’s move onto the changeup.

Spin Rate of Changeups

The table below depicts average vertical movement, horizontal movement, swinging strike percentage, and contact percentage for each range of spin rates.

Changeup and Spin Rates

Changeup and Spin Rates

High spin rate means more movement for the changeup, in both the vertical and horizontal direction.

However, more batters swung and missed on the lower spin-rate changeup.

What we deduced is that the higher spin rates correlate with increased movement, that can often freeze a batter. We will have to add this to our ongoing research reel to validate our hypothesis.

The other concept we would like to further study is the type of contact (hard, medium, soft) for different changeup spin rates (including exit velocities).

Spin Rate of Curveballs

The table below depicts average vertical movement, horizontal movement, swinging strike percentage, and contact percentage for each range of spin rates.

Curveball and Spin Rates

Curveball and Spin Rates

High spin rate means more movement for the curveball, in both the vertical and horizontal direction.
However, more batters swung and missed on the lower spin-rate curveball. Also, less batters hit the low spin-rate curveball.

Interesting…

Similar to above what we deduced is that the higher spin rates correlate with increased movement, that can often freeze a batter. We will have to add this to our ongoing research reel to validate our hypothesis.

The other concept we would like to further study is the type of contact (hard, medium, soft) for different curveball spin rates (including exit velocities).

The other concept that would be extremely difficult to study, is pitch usage. What we mean, is how much more effective is a curveball after a fastball, compared to after a changeup.

Oh, that would be a glorious study. Maybe it is something that the Philadelphia Phillies already know since they put a priority on curveball spin rates.

Spin Rate of Sliders

The slider spin rates follow what we would expect.

The slider has a lot of horizontal spin, which means that horizontal movement is primary to vertical movement.

For more information on how the Magnus Force impacts the slider click here.

Slider and Spin Rates

Slider and Spin Rates

This is great data, high spin rate positively affects horizontal movement, swinging strike percentage, and contact percentage. More spin equals more success, for the slider at least.

The Final Summary Table

Let’s recap the entire article.

Spin rate helps increase movement in a particular direction, unless the arm slot counteracts assumed convention for each pitch type.

Spin Rate Summary

Spin Rate Summary

Increased spin rate correlates with higher percentages of swinging strikes for the four-seam fastball, two-seam fastball, and slider.

Increased spin rate correlates higher percentages of contact for the four-seam fastball, two-seam fastball, and slider.

To further hammer home the concept of spin rate we need research strike percentages for each pitch type and type of contact.

We hope you liked our study.

Note this article was researched by Blake Talley with edits and commentary by Ricky Mears.

*Data was obtained from FanGraphs, Baseball Reference, and Baseball Savant.

Please note: This post contains affiliate links.