Does Your Youth Pitcher Keep Missing the Strike Zone with Their Fastball? Slider Spin May Be Why!

Written By: Dave Shinskie

Identifying Slider Spin

Does your son or daughter have slider spin when throwing a fastball? A common problem in youth baseball is not informing kids that slider spin on a fastball is not ideal for throw/pitch efficiency.  How can you identify if your son or daughter has slider spin on the ball in their throws? First thing is knowing what you are looking for when you're playing catch in the backyard. If your son or daughter is a righthanded thrower, the first good indicator of slider spin is YOU may be catching the ball on the right side of your body consistently pulling the throws across your body.  A slider has a clockwise rotation and spins on an axis that faces to player indicated by the blue line in the gif below. When playing catch you will be able to identify slider spin by seeing a circle in the middle of the ball. For righty or lefty throwers a 4 seam fastball should have close to perfect vertical spin/12 o'clock to 6 o'clock spin. A  2-seam fastball’s axis, in comparison to a righty, points towards 11 o’clock.  For young kids slider spin when throwing a 4 seam fastball is not horrible for them but can become a bad habit to break. Plus we want to have the correct spin on the ball, especially as a pitcher. In this article, we will identify slider spin, what causes it, and how we can help eliminate it from 4 seams and 2 seam fastballs.

           Slider Spin

           4 Seam Spin

            2 Seam Spin

What Causes Slider Spin

The main culprit that causes slider spin is the release point of the middle finger off a fastball grip. Most the time kids can't help throwing the ball off the middle finger because:

  1. The middle finger is their dominant finger and longer than the index finger.
  2. Young kids tend to throw with three fingers, with a tendency to release on the side of the ball, again off the middle finger.
  3. Their arm swing doesn't allow them to get on top of the ball. This is when mechanics play a role in causing slider spin.
  4. Kids, Parents, and Youth Coaches don't have the knowledge on how to teach the throw and release of the ball properly. This is the problem with many my youth pitchers.

A 4 seam fastball is the most common pitch and the ideal grip for a position player as well on the transition from glove to hand. WHY? Because at release point the finger causes backspin on the baseball. The result is the ball does not drop as much as otherwise, without backspin. In other words, a 4 seam fastball is really appearing to defy gravity and travel more in a straight line. A 2 seam fastball is thrown with similar backspin but again on 11 o'clock axis.

This is a 4 seam fastball. You can see the pitchers' fingers rip through through the ball to create backspin almost making the seams on the baseball invisible.


You can see the spin of the ball off the fingers of the pitcher creating backspin on an 11 o'clock axis. This makes the ball tail in or run away from the hitter.

The Magnus Effect

The pitcher is taking advantage of the Magnus Effect when throwing a fastball. The Magnus Effect is when a spinning sphere effects the air pressure around it. The side of the baseball spinning with the direction it is traveling moves against the air faster, creating more drag and pressure on the ball which causes the air to push on it. On the opposite side of the ball, air pressure is reduced which makes the ball travel easier in that direction when a spinning sphere effects the air pressure around.


When throwing a curve or slider the Magnus Effect is being taken advantage even more than fastballs. The topspin of a curveball and the side spin of a slider makes the ball drop and cut. Both grips and releases cause the seam to push air around to change the pressure on the ball.

This is a slider. You can see the pressure being put on the middle finger. The release point is more on the side of the ball which creates a clockwise spin that will make the pitch drop on its way to home plate.


How Can We Fix It

Asking if a kid can see that slider spin is occurring is a common question I will bring up in lessons. Having a thought process and feeling with what they are doing is something that he or she can control and fix from throw to throw but it is not often taught. We like to have kids visualize and react to what is being said and into what is being felt. When trying to recognize the slider spin, the catcher should be able to see where the thrower is missing with his fastball. Seeing the ball out of the thrower's hand and knowing that a slider has clockwise spin on the baseball you will be able to clearly tell that they released the ball wrong.

The arm swing and finish is the hardest thing to correct in a thrower besides having a feel for which finger the ball is coming off of through the throw. Lucky Baseball Rebellion has developed some fairly simple concepts to allow your child to efficiently enhance upper body mechanics and arm swing.  Here is a #TransformationTuesday tweet from Baseball Rebellion showing how a forty minute lesson can help your son or daughter with arm swing mechanics.

Being able to identify if your son or daughter is trying to throw a 4 or 2 seam fastball and throwing a slider instead is also key. They are different spin axises that affect a consistent ball path. So when playing catch learn how to pay attention to spin on the baseball along with consistent movements. Ask your son or daughter what they are feeling on a throw to throw basis. What finger did the ball feel like it came off? Did you see the spin on the ball? Where was your eyesight? Your arm swing looked a little stiff, did you feel that?

In conclusion, clearly, the seams on a baseball have a huge role in affecting the flight of the ball.  Learning how to create correct spin needed to give a throw/pitch the highest potential for success is huge in developing effective throwers.

This is something we can now measure here at Baseball Rebellion. Our new Rapsodo is a great tool that measures and tracks Velocity, Total Spin, Spin Axis, Spin Efficiency, True Spin, Strike Zone Analysis, and Vertical and Horizontal Break. It is an amazing product that can pinpoint adjustments needed to be made to improve any baseball throwers.


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