Understanding Advanced Pitching Metrics

Advanced analytics in baseball continue to evolve and become more popular, and with that new ones are becoming commonplace within broadcasts and other coverage. These started as new ways of evaluating the results of plays, and have now evolved into analyzing the physics of the components inside of that play. The earliest popular forms of these metrics focused on hitting, and I’ve previously given an overview of how launch angle could impact results. The next set of metrics gaining popularity now are those around pitching - below is an overview of the key metrics and what they can mean for success.


Spin and Movement Metrics


Spin Rate


This is the most prevalent of these metrics so far, but also one of the most straight-forward. Spin Rate is the measurement of how often the ball is making a full rotation, measured in revolutions per minute (RPM). A higher spin rate on an otherwise equivalent pitch will mean more movement.


For breaking pitches, the impact of this is obvious - more RPM and more movement means a bigger break on the pitch. For fastballs this can be a little more complicated - the spin on a fastball is primarily backspin that’s acting against gravity. Gravity is still the stronger force, but a four-seam fastball thrown with more spin will drop less. How this alone could impact the location of the pitch can be seen below.

There are a couple important clarification points here that tie together:

  • A lower fastball spin-rate does not mean a pitcher can’t be effective. What it does mean is that a pitcher would likely want to work their fastball in the bottom of the zone. The ball is going to drop more than a batter will anticipate, and hopefully generate more ground balls.

  • This is part of the reason why we’ve seen more pitchers work up in the zone. With more hard throwers who possess a higher spin rate, working low in the zone is more likely to generate extra base hits as it works into the sweet spot of the bat. Working up with a pitch that doesn’t drop as much as a hitter will naturally expect generates more swinging strikes.

Understanding who a pitcher is using spin rates is effective to building a game plan, and can also be beneficial in scouting as these tools become more widely available to create profiles. Meanwhile, it could also open up inefficiencies for some teams to exploit - the focus on higher spin rates could allow teams to identify and sign pitchers who don’t have those underlying metrics but are still able to be successful.


Spin Axis/Tilt


Spin axis and tilt both describe essentially the same thing - which way the ball is rotating when looked at from the pitcher’s point of view. The biggest difference between the two is primarily how they’re measured - tilt uses the terminology of a clock, while spin axis measures in degrees. The tilt nomenclature tends to be used more often, but spin axis provides the advantage of numbers that can be more easily manipulated to do evaluations.


An example of a four-seam fastball thrown by a right-handed pitcher is below.

The pitch is thrown with almost entirely backspin, though it does have a little bit of tilt to the right. From a tilt standpoint this would be described as 12:30; for spin-axis it would be described as 195. This pitch would primarily have backspin that fights against gravity, as well as some movement to the right. In comparison, a 12-6 curveball would have a tilt closer to 6:00 that works with gravity to increase the vertical drop.


The spin axis is primarily determined by the positioning of the pitcher’s hand at the time of release, and therefore is able to be changed to design a pitch more easily than spin rate can be. The axis of a particular pitch will drive movement based on their arm angle and other release metrics is essential, especially for understanding how that pitch will fit into a pitcher’s repertoire if they’re working on adjusting or adding a pitch.


Spin Efficiency


Spin efficiency is the measure of how much of a pitch’s spin is useful spin that is increasing the movement of the pitch. To understand that, it’s important to cover that we previously discussed how the spin on a pitch could differ depending on how much of it is up and down vs side to side. However, there is one additional way a pitch could be spinning.


If we go back to the clock from the prior example, a pitch’s spin could also be similar to rotating around the outside of the clock - think of the spin a football would have if looking at it from behind the quarterback. This is called gyrospin, and even though it decreases spin efficiency it isn’t always a bad thing; for example, some of the best sliders will have a high proportion of gyrospin.


Spin efficiency is calculated as the percentage of the total spin that is useful spin (transverse spin). This can then also be combined with spin rate to determine a “true” spin rate. In turn, that is useful to pitchers, pitching coaches, and evaluators in exploring the expected effectiveness of pitches, as well as to help identify what’s wrong if a pitch suddenly loses its success.


Release Metrics


In addition to the spin metrics above, a pitch is also impacted by where it’s released. That can be evaluated primarily through the below metrics.


Release Height/Side


This is straight-forward, evaluating how high and how far to the side a pitch is being released. In addition to impacting the spin and path of the ball, this will also change how a hitter sees the ball coming out of the hand.


Extension


Extension measures how far in front of the rubber a pitch is being released. This directly impacts timing, as a pitch thrown with the same velocity but released a foot closer will get to the hitter faster than expected.


These two release metrics can be important for a team in understanding how their staff fits together as a whole. The Rays in particular took this approach to heart - throughout a game, a hitter would not see the same release angel or extension from multiple pitchers. This makes it very difficult for a team to gain their timing and get comfortable throughout the game, and is the type of advantage that a team at a financial disadvantage can use to improve results.



All of these metrics are useful, but they really tell a story when evaluated as a whole to understand a pitcher's stuff and how it fits in with the rest of their team. While these metrics are still evolving and more is being learned about the tools, it’s essential that teams and players understand how they can be used to improve. Meanwhile, hopefully this has given enough of an overview to understand it from a fan’s point of view as they become a bigger part of the game’s nomenclature.


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