Why Don’t Pitchers Know How to Throw a 2-seam Fastball?

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

For eons pitching coaches have been showing young pitchers how to throw a 2-seam by rotating the baseball from a 4-seam grip to a 2-seam grip and telling them to go-ahead and chuck the ball.  The implication being that a simple rotation of the ball in the hand along a different set of seams will create the desired movement. Unfortunately, we’re going to bust that myth today and throw away years of pitching instruction!

Tech is here to help us learn how to throw a 2-seam fastball.  It’s meant to have just a little less velo than a 4-seam, but break more laterally, towards arm-side.  However, most pitchers (at least in our universe and we are willing to bet everywhere) can’t throw a good one.  After some basic research with Rapsodo and a high-speed camera, we can tell you with 100% certainty it’s not the pitchers fault.  Unfortunately, unbeknownst to most pitching coaches, the seams alone don’t create the movement.  Something else is responsible for it.

We aren’t here to lay blame on anyone.  Who knew?  Well, Dr. Alan Nathan did.  During an interview with Fangraphs (11/5/2013), Dr. Nathan (University of Illinois, THE baseball physics dude… Lol) said “I’m relying on laboratory experiments that seem to show that all other things being equal, a four-seam pitch and a two-seam pitch, if the spin axis were oriented exactly the same, would break exactly the same.”

Think about that for a second!  Back in 2013, he was basically saying that if the baseball is held differently but released similarly to generate the same spin axis, then both the 4-seam and 2-seam pitches will break the same way.  This basically implies that generally the seams may have little to do with ball movement.  So, we tested it here recently at RPP.  The following is a summary of our findings.

Regular 2-seam – Here is the data and high-speed video from an actual 2-seam.  We labeled this “Aviles Pitch A: 2-seam”:

    • Total Spin: 1768
    • True Spin: 1767
    • Spin Efficiency: 100%
    • Spin Axis: 01:34
    • HB / VB: 15.1 in / 14.1 in.

2-seam w/ 4-seam Grip – Here is the data and high-speed video from our Myth Buster pitch (pitching cue was “think about throw a 2-seam while holding a 4-seam grip”):

    • Total Spin: 1780
    • True Spin: 1780
    • Spin Efficiency: 100%
    • Spin Axis: 01:36
    • HB / VB: 15.0 in / 13.7 in.

Here is the data side-by-side, including a regular Aviles 4-seam pitch.  As you can see, so long as you release the ball the same way off your fingertips to generate the same spin axis, you can create similar movement by throwing a “2-seam pitch w/ 4-seam grip” as a regular “2-seam pitch”.

Here is a better visual of both pitches along with a regular Aviles 4-seam (in blue):

Our Myth Buster pitch (yellow) has basically identical movement to a regular 2-seam pitch (red, hiding behind the yellow).  What does that tell you? It basically says that the orientation of the seams by themselves don’t necessarily generate the direction of movement.

In a prior article “Pitch Development and Design… What is Relative Movement?”, we reviewed how spin axis determines the direction of movement.  So, if you want to throw a 2-seam and it makes you feel better holding the ball like a 2-seam then god bless, but make sure you tilt the axis to get the results you’re looking for.

So, why do so many 2-seams suck? Because young pitchers haven’t been taught how they can tilt the axis for various pitches.  Rotating the ball along the seams by itself doesn’t create a 2-seam. Myth Busted!