What Is Spin Rate? Fantasy Baseball Sabermetrics Glossary and Definitions

What is spin rate and how to use sabermetrics for fantasy baseball? Definition, meaning of spin rate for pitchers as part of our sabermetrics glossary.

Welcome RotoBallers to our overview of Spin Rate. This article is a deeper dive into spin rate and is part of our ongoing series "Using Sabermetrics for Fantasy Baseball."

In this article, we'll explore the benefits of high and low-spin fastballs and identify which secondaries are more effective with more or less spin using everyday terminology and real-world examples. We'll also look at Active Spin and how it can render raw spin measurements misleading.

You can find our entire sabermetrics glossary, which includes links to many other sabermetric stats as part of this series. Each stat deep dive will be released over the next few days. Stay tuned!

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What Is Spin Rate? Sabermetrics Glossary

Spin rate has become one of the most recognizable Statcast metrics, with supporters of a given pitcher often highlighting his spin rates to make their case.

Unfortunately, the baseball world has done a lousy job conveying what spin rate means. Many fantasy managers know spin rate exists, but few use it to improve their rosters as a result.

The best place to find spin rate is the Baseball Savant Leaderboard. Select "Pitch Arsenals." It defaults to pitch velocity, but you can click on it to select "Average Spin" to get the information you want. If you wish to look up a specific pitcher, you can instead type their name into the search bar at the top-right of the page.

Active Spin is its own leaderboard category, and we look at it below as well.

How to Interpret Spin Rate

Spin rate is measured in RPMs, or Rotations Per Minute. Each pitch type has its own baseline numbers, so a high-spin fastball might have an average spin rate for a curve. Comparing different types of pitches by spin rate is pointless, so focus on how any given pitcher's offering compares to the same pitch type thrown by other arms.

So, are higher or lower spin rates better? The answer is that it depends on the type of pitch you're looking at. Let's start with fastballs.

The average spin rate for fastballs ranges from 2,100 RPM to 2,400 RPM. Heaters with spin rates above this range tend to have "late-life" and induce more whiffs than your average heater. They usually have backspin, or spin against gravity, which guides the ball weakly into the air if contact is made. This allows them to post elevated pop-up and suppressed HR/FB rates to complement their whiffs.

Joe Musgrove led all MLB starters in four-seam fastball spin with 2,635 RPM in 2024. That's a bit misleading, though, as not all of Musgrove's spin meaningfully contributed to the pitch's movement.

We have to consider "gyro spin," alternatively called "useless spin." If you've ever seen a bullet in slow motion, it rotates slightly while flying straight to its target. That rotation is gyro spin, and it doesn't impact where the bullet ends up. A metric called "Active Spin" measures how much spin actually affects the ball's trajectory.

Musgrove posted an Active Spin of 63.1 percent on his fastball last season, ranking 633rd among qualified pitchers. Musgrove's fastball generated plenty of whiffs with a 10.8 percent SwStr%, but he got there by throwing it outside of the zone (49.6 percent Zone%) rather than relying on late life.

Batters posted a 45.3 percent FB% against Musgrove's fastball last season, and its 17.2 percent IFFB% was strong. However, hitters also produced a 20.7 percent HR/FB against the pitch, leading to far more homers allowed than Musgrove wanted. Musgrove's high spin rate didn't make his fastball elite thanks to a low Active Spin.

Spin rates below the average range lend themselves to contact management. Low-spin fastballs produce weakly-hit grounders and a lower slugging percentage than their high-spin counterparts.

Ranger Suarez illustrated this approach nicely last year, as his 2,010 RPM was among the lowest among qualified pitchers. Its Active Spin of 79.1 percent ranked 559th among qualified pitchers, further limiting movement.

This profile offers less fantasy upside due to the lack of strikeouts but can be a great way to log innings without jeopardizing your ratios.

The Importance of Active Spin

Active Spin made Musgrove's fastball play down, but the inverse can also be true. For instance, Michael Wacha doesn't possess a great fastball at first glance. He averaged 93.6 mph (42nd percentile) on the radar gun last year, and its 2,131 RPM spin rate is below the average range.

However, Wacha's heater had an Active Spin of 99.2 percent. As a result, the pitch played like a high-spin heater with a 44.9 percent FB%, 25 percent IFFB%, and 8.3 percent HR/FB. It's an important weapon for him despite its average 7.1 percent SwStr%.

Spin rate is useful, but looking at Active Spin, too, provides a more complete picture of how spin may affect a pitcher's performance.

Evaluating Spin Rate on Secondary Offerings

Breaking pitches usually want high spin rates. Unlike fastballs, breaking offerings have topspin, or spin toward the ground, which can help guide the ball down if contact is made. Breaking pitches tend to be a pitcher's strikeout offering, though, so we generally don't want contact on them. Breaking ball spin rates are, therefore, the least important.

Changeups and knucklers are generally most effective with low spin rates, so they move more. However, pitchers may run into issues if an offspeed pitch's lack of spin helps batters differentiate it from the rest of their arsenal.

There are enough variables in play that spin rate should never be considered alone. Instead, start with Pitch Info and then use spin rate to confirm if a given pitch can sustain its performance or if it was probably a fluke. The table below provides a baseline to compare repertoires to:

Conclusion

Fastballs can be good with high or low spin rates, but higher spin tends to translate better to fantasy. Breaking pitches typically benefit from higher spin rates. Changeups want as little spin as possible to maximize their movement. Finally, gyro spin can distort spin rate readings, meaning you should always combine spin rate with other metrics in your analysis.

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