Pitch Development and Design… Sliders – Part 4

By Bahram Shirazi (BSEE, MBA, Co-Owner RPP) and Robbie Aviles (RHP Cleveland Indians, Pitching Lab Coach)

With all the talk around spin rates, we sometimes forget that at the end of the day pitching is all about velo and movement.  Unlike fastballs (click here) and change-ups (click here), sliders and curveballs tend to break towards the glove side.  They are generically referred to as breaking balls, and although most talk about them in similar terms they behave very differently from one another.

Sliders generally have a lot of gyrospin, some sidespin and either underspin or topspin.  They sit closer to the gyro zone than any other pitch.  The following table provides some context for sliders vs. change-ups and 4-seams.

a) Statcast: Baseball Savant and RPP estimate of True Spin and Efficiency.
b) BP: Pitching Backward: Spin That Curveball by Jeff Long (7-23-15).

The one thing that stands out is the decline in True Spin and Spin Efficiency as we go from a fast ball to a change-up to a slider.  This generally implies increased gyrospin and a tighter movement along the corresponding spin axes from pitch type to pitch type.

It is also important to highlight the corresponding drop in Velo and Spin Efficiency from a 4-seam to a slider.  An 8-mph velo drop seems to equate to an approximate 70% point drop in Spin Efficiency, or approximately 1 mph per 10% points of drop (more on this in a later article).  Here is a summary of what we like, and don’t like, to see in a typical slider:

What we like to see:

    • Spin efficiency around 15% to 35%
    • Relatively consistent spin axis from pitch-to-pitch
    • Consistent spin efficiency
    • Velocity drop vs. 4-seam of about 5-9 mph
    • Greater horizontal drop then vertical of fastball
    • Being able to throw for a strike and below or out the zone consistently
    • Movement to be glove-side
    • Fastball arm speed

What we don’t like to see:

    • Spin efficiency higher than 35%
    • Somewhat inconsistent spin-axis from pitch-to-pitch
    • Velocity drop of more than 10 mph
    • Somewhat inconsistent spin-efficiency from pitch-to-pitch (the more inconsistent the spin-axis and spin-efficiency, the more inconsistent the break.  This in turn implies less overall command of the pitch)

Now let’s talk more specifics… When you ask a high school pitcher what type of breaking ball he throws, you may get different answers.  Surprisingly, many say they have a curveball, but the data actually shows it to be a slider or even a slurve.  As a pitcher it’s important to know exactly what you have.  Below is an example of a slider with a Spin Rate of 2020, 27% Spin Efficiency and break of -4.6 VB / 2.3 HB.  This would be a slider with a good amount of gyrospin (screenshot courtesy of Rapsodo):

Sliders aren’t generally known for their extreme movement (although some do, as you begin to get into the slurve territory).  Sliders are thrown harder than a curveball with a tighter break and less Magnus Force to speak of, given the high amount of gyrospin.  Hence, gravity does what it’s supposed to do as it pulls the ball down towards the ground at a rate of 9.8 m/s^2 (the force gravity pulls on any object).  This results in what folks observe as sharp drop and what appears to be a “break”.  Given the limited backspin on this slider, the ball drops substantially quicker than a typical fastball.  Here is the high-speed video of the same pitch in the chart above (the gyrospin is pretty apparent):

(Slider – Spin 2020, True Spin 551, 27% Spin Efficiency)

You might ask… “well then why would a slider be effective if it has less movement than other pitches?”  A great question.  Well, as we have said before the art of pitching is all about deception.  No single pitch thrown over and over in sequence would be successful as the batter gets used to its movement.  The idea is to have different pitches with different degrees of movement thrown in a mix.  In the case of a typical slider you are throwing a ball with less movement than most, and gravity is pulling on it with less negating Magnus Force.  So, it’s going to “break” and drop quicker than a typical fastball with usually has a rise component due to back spin.

Alternatively, if you aren’t happy with your slider’s movement, you can set out to do what Trevor Bauer did this past off-season.

Bauer’s New Slider –  This past winter Bauer, looking to improve his slider, set out to create one with more lateral movement like Marcus Stroman and Corey Kluber’s.  Although we aren’t privy to his thinking, looking at Pitch/Fx data on the Brooks Baseball website may explain why.

Stroman and Kluber, both have significant lateral movement (right to left) on their sliders (6-8 inches).  This in turn appears to have given them relatively high “Swing / Miss %s” (49.8% for Kluber), and lower “Batting Average Against” stats (.112 for Kluber).  As an aside here is a great article on Kluber’s slider/curveball.  So, Bauer set out to increase his slider’s lateral movement:

According to Brooks Baseball, so far this April, Bauer has thrown 16 sliders with a -6.76 HB and -0.72 VB.  That lateral movement is more than 2x what he was getting in 2017.  Here is recent video on Kluber and Bauer’s sliders:

(Corey Kluber vs. Trevor Bauer’s New Slider)

Bauer may or may not stay with this pitch.  It all depends on how it works for him but the punch line is that pitch development and design is here to stay.  As the new technology takes hold, and more and more folks understand the data, committed pitchers will take the time to learn this type of information and put it to use.

Just in case you are wondering how to get more lateral movement on a pitch? Here is a list that frankly doesn’t do it justice, but nonetheless attempts to review what would be involved:

    • Slight grip change
    • Adjustment in the final release of the ball
    • Applying appropriate spin axis closer to 09:00
    • Less gyrospin and more sidespin (higher Spin Efficiency)
    • Working with a trained coach who understands the data feedback and can cue adjustments
    • Trial and error with Rapsodo and high-speed video feedback

The images below compare an Aviles “Slider” with -4.6 HB and to an Aviles “Slurve” with lateral movement at -13.4 HB, with a spin axis closer to 09:00.

Note: Although the Pitch/Fx movement info presented earlier is directionally comparable to Rapsodo data, the actual amount of movement amount is not 100% comparable.

With pitching, it’s impossible to say that if something works for one pitcher that it will also work for another.  There are way too many variables.  However, the reality of present day is that new tech such as Rapsodo and high-speed video cameras (1,000 fps or higher) can help pitchers develop more quickly and effectively.  Through trial and error and the help of a qualified coach, young pitchers can further develop and advance their pitching arsenal.  The challenge is understanding what the data is telling you and knowing how to cue it and apply it in training.

Next up… south of the border with curveballs…

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