Spin Rate: Using Sabermetrics For 2024 Fantasy Baseball

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

Unfortunately, the baseball world has done a lousy job of conveying what spin rate really means. The result has been a ton of fantasy managers who know spin rate exists, but few who use it to improve their rosters. This article will teach you everything you need to know to fold spin rate into your pitcher evaluations. We'll also illustrate the efficacy of spin rate using Pitch Info data from actual pitchers.

The best way to look for spin rate is to go to the Baseball Savant Leaderboard and 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 want 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. Let's get started!

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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 try to 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 rates to complement their whiffs.

Eury Perez led all MLB starters in four-seam fastball spin with 2,635 RPM in 2023. That's a bit misleading though as not all of Perez'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 has no impact on where the bullet ends up. A metric called "Active Spin" measures how much spin is actually affecting a ball's trajectory.

Perez posted an Active Spin of 94.8% on his fastball last season, a number that sounds pretty good. However, the pitch ranked 199th among qualified pitchers by Active Spin. Perez's fastball had an 8.4% SwStr%, which is good but not great. It was put into the air frequently with a 58.3% FB%, but its 14.3% HR/FB led to more big flies than Perez would've liked. Perez wasted some of his RPMs.

If you're looking for a contact manager instead of a strikeout artist, you want a spin rate below the average range. Low-spin fastballs produce weakly-hit grounders and a lower slugging percentage compared to their high-spin counterparts. Ranger Suarez illustrated this approach nicely last year, as his 1,976 RPM was among the lowest among qualified pitchers. Its Active Spin of 85.5% ranked 457th among qualified pitchers, further reducing movement.

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

The Importance of Active Spin

Active Spin makes Perez's fastball play down, but the inverse can also be true. For instance, Erik Swanson doesn't possess a great fastball at first glance. He averaged 93.7 mph on the radar gun last year, and its 2,266 RPM spin rate fits squarely into the average range. Its 45.6 Zone% didn't even help him get ahead in the count.

However, Swanson led MLB pitchers with an Active Spin of 99.6%. As a result, the pitch played like a high-spin heater with a 9.8% SwStr%, 53.3% FB%, and 12.5% IFFB%. It's an important weapon for the reliever.

Spin rate sometimes tells the whole story, but looking at Active Spin too provides a more complete picture of how spin affects 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 given pitcher's strikeout offering though, so we generally aren't looking for contact on them. Breaking ball spin rates are therefore the least important to look at but may provide interesting information at times.

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 elite performance or if it was probably a fluke. The table below provides a baseline to compare repertoires to:

Conclusion

To summarize, 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 that you should always combine spin rate with other metrics in your analysis. Stay tuned to learn more about how analytics can help you dominate your fantasy baseball leagues in 2024!