Why “Clustering” Is Important for Pitchers

By Mike Lembo (BS Exercise Science, Pitching Coordinator at RPP)

The Rapsodo Pitching camera provides an incredible amount of information by pitch type.  Just as relevant, however, is how each individual pitch behaves versus the others.  In evaluating our pitcher’s ball movement charts, we generally work with them to develop what we refer to as “clusters”. They form when a pitcher can consistently repeat the spin axis and direction by pitch type.

If a pitcher can throw in very tight clusters, then we know that he can replicate consistent movement patterns.  When switching between pitches, we want to see the clusters spread apart on the movement chart.  This is one of the most effective ways to be successful as a pitcher and it actually speaks volumes about a pitcher’s capabilities on the mound.  The movement chart below provides a good example of clustering:

pitch clustering

This movement pattern is from one of our college-level pitchers. You can reach the following conclusions from this movement chart.  He can…

    • Replicate movement on several pitches on a consistent basis
    • Create movement patterns in different locations on the chart for each pitch
    • Change spin direction on five distinct pitches
    • Create movement on his pitches that are different from his arm slot
    • Control three distinct off-speed movement pitches

Now, let’s look at a less experienced high school pitcher:

From this movement pattern we can determine that he:

    • Has difficulty creating consistent movement (clusters), for example his 4S Fastball has a very inconsistent pattern
    • May struggle with location/throwing strikes due to an inconsistent release point and mechanics
    • Has inconsistent vertical or horizontal break, depending on the pitch
    • Has a tendency to blend his slider and curveball

Whenever we have a new athlete come in for pitch design, initially we collect a baseline for every pitch. Generally, we see pitchers with movement patterns like the chart below.  The top right quadrant has two pitches (FB, 2S), and both are grouped closely together that move relatively in the same manner.

The table below summarizes the ranges from his baseline assessment for the fastball and 2-seam in terms of spin direction, horizontal break, and vertical break.  You can definitely see overlap in the vertical breaks.

The first step for creating clusters is addressing spin axis and direction to add more tilt onto a pitch (in this case it was the 2-seam), which in turn, increases horizontal break and decreases vertical break. Once we find a comfortable range with spin direction with his 2-seam, we begin to see a movement pattern away from his fastball.

We continually experiment with spin direction to find an adequate amount of movement that will be complementary to the fastball. The final step is repetition, repetition and more repetition until the movement begins to become ingrained. Then, through consistent mechanics and release, we will see clusters of pitches in a new location on the movement chart.  Let’s see what he was able to do when we made those changes, fastball on the left and 2-seam on the right.

After two months of regular pitch design sessions, our high school pitcher was able to:

    • Add an hour of spin direction to his 2-seam
    • He now sits consistently at approx. 16 inches of horizontal break on his 2-seam and decreased vertical break by about 5 in
    • He was able to better cluster his fastball near the :50 spin direction
    • By alternating spin direction between the fastball and 2-seam, he created two distinct movement patterns and became particularly good at repeating those spin axes

In an ideal world, we want spin direction for a certain pitch to be within :5-10 minutes for every repetition.  Many of the more experience pitchers that throw at our facility are within only a few minutes for each pitch-type.

To summarize, creating clusters is all about the consistency of the spin axis across your pitches.  Keep an eye on that magical number and soon enough you will develop a feel for how to cluster your pitches.

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