How to Throw a Curveball

how to throw a curveball

In spring of 2018, high school senior, 6’6” 200, LHP Matthew Liberatore was selected 16th overall in the MLB Draft by the Tamp Bay Rays.  According to Rapsodo, his curveball had a total spin rate of approximately 2800 rpm with a 99% spin efficiency.  Thrown in the low to mid-70’s mph, it had a vertical drop of 24 inches (2 feet).  His stats and data were posted on social media, along with commentary that noted the spin rate on his curveball had an additional 500 rpm’s vs. the MLB average.  As curveballs go, a 24 inch vertical drop and 2800 spin rate are up there.  So, let’s get into it, how to throw a curveball…

    • Overview
    • The Grip
    • How to Throw a Curveball
    • Curveball Data
    • Movement Chart
    • What We Like to See and Don’t Like to See

Here we go…


As reviewed in our other articles, curveballs and sliders tend to break glove side.  Although both are generically referred to as breaking balls, they behave very differently from one another, with the slider possibly having the least movement of any pitch (relative to the gyro) and the curveball potentially the most.

Having a breaking pitch is an essential component to a pitcher’s arsenal. It helps keep hitters off-balance and unable to commit to setting up exclusively for fastballs.  The slider and curveball are sometimes referred to interchangeably. But data shows it can be nothing further from reality.  Sliders generally have lateral spin and some degree of backspin or topspin with less overall movement.  While curveballs generally have mostly topspin and some amount of lateral spin with lots of movement.  There is also an area in between the two referred to as the Slurve.  But the slider and the curveball are nothing alike.  They break differently and have very different movement patterns.

The following is a summary of major league breaking balls and 4-seam fastballs’ average velos and spin rates.  The one thing that stands out is the decline in spin efficiency as we go from a fast ball to curveball and then a slider.  A curveballs spin efficiency generally sits right in between a fastball and a slider, generally in the 65% range.

how to throw a curveball

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

The Grip

Grip is an integral part of how to throw a curveball.  So, let’s get into how you grip one, what it looks like in high speed at the point of release and what data analytics tells you about the pitch.  Here is a good example of a typical curveball grip:

how to throw a curveball

(Curveball Grip)

How to Throw a Curveball

The following is high speed video footage from the Point of Release for Dom Cancellieri’s curveball (Bergen Catholic RHP).  The total spin rate on this pitch is 100+ rpm higher than average MLB curveball.   Throwing a curveball is much about the grip, extension at release and the release point itself.  As you can see the fingers on top at the release point help create the top spin that creates the curveball’s downward magnus force and movement.

(Dom Cancellieri Curveball)

Curveball Data

A 12-6 curveball with a 06:00 spin axis has pure topspin.  This would be the opposite of a 4-seam fastball with a 12:00 spin axis which would have pure backspin. The net result of all that topspin on the curveball is Magnus Force that helps it drop quicker than expected by increasing the air pressure on the top-side of the ball.

The following is a summary of the Rapsodo data on the above video, with top view and side view further below:

    • Speed: 70 mph
    • Total Spin: 2431
    • True Spin: 1697
    • Spin Efficiency: 70%
    • Spin Axis: 06:38
    • Movement: -5.4 HB / -16.2 VB

The solid red lines in the image below depict the actual path of the ball.  The dotted lines represent the gyroball (no movement) path.


Since the objective is generally to create as much movement as possible, the higher the “true” spin rate the bigger the break. Depending on how the ball is released a curveball could drop straight down (12/6) or have some degree of lateral break as well. A curveball thrown with some lateral break will generally rotate some around the z-axis (below) and create more lateral movement and horizontal break.  This generally is a result of spin axes in the 07:00 – 08:00 range vs. 06:00 – 07:00 range.  Here is a good image on the three axes and directional movements of the ball.

blankThe following chart provides a summary of several curveballs from program with good examples of more and less horizontal break by various pitchers.  Spin axes range from 06:32 through 08:04.  As you can see, given somewhat similar spin efficiencies at the extremes, with different axes you can get substantially different directional movements on the curveball.

    • 08:04 Spin Axis -> 14.6 in HB / 7.9 in VB
    • 06:32 Spin Axis -> 5.6 in HB  / 20.5 in VB

how to throw a curveball

Movement Chart

The following pitch movement chart reflects the movement of the curveballs listed above by pitcher.

how to throw a curveball

What We Like to See and Don’t Like to See

Here is a brief summary of what we look and don’t like to see in curveballs:

How to throw a curveball – What we like to see:

    • Spin efficiency at 65%+
    • Relatively consistent spin axis from pitch-to-pitch
    • Consistent spin efficiency
    • Velocity drop vs. 4-seam of about 10-15 mph
    • Greater VERTICAL drop than HORIZONTAL
    • Being able to throw for a strike and below or out the zone consistently
    • Movement to be glove-side
    • A swing and miss pitch

How to throw a curveball – What we don’t like to see:

    • Spin efficiency lower than 50% (as it begins to approach a slider)
    • Velocity drop in excess of 16+ mph
    • Lack of full intent as it’s meant to be fastball arm speed
    • Somewhat inconsistent spin-axis from pitch-to-pitch
    • 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)

So, there it is… how to throw a curveball pitch.  If interested in this series of articles on how to throw different pitch types, please click here.

By Bahram Shirazi (BSEE, MBA, Co-Owner RPP)