Pronators vs. Supinators

Pronators vs. Supinators; What Are The Differences?

If you’ve been around baseball for a long period of time, you’ve probably picked up on the fact that every pitcher looks and throws differently. While this is true, pitchers can often be grouped into categories that make them easier to understand. One of these differences is whether the pitcher is a pronator or a supinator. 

Definitions

To start off, being a pronator means that the pitcher’s throwing arm is biased to turning their palm inwards towards their body, or counterclockwise for a right-handed pitcher. That is, if the palm is facing upwards in the supine position. If a pitcher is a supinator, it means the opposite. The pitcher is biased to turning their throwing arm clockwise for a right-handed pitcher, or away from their body. 

Now that these definitions are laid out, we can start to talk about why this is important to pitchers. It is important to note that every pitcher is grouped in either one of these categories. Some pitchers can do both, but every pitcher is biased to one or the other. Both of these biases are important to pitchers because it shows what pitches they are able to throw well, and what pitches they might struggle with. 

Pronators 

Pronators are superior at throwing fastballs that run to the pitcher’s arm-side, like sinkers, 2-seams, and backspun fastballs. They are also able to throw changeups more easily than a supinator. On the contrary, pronators are going to struggle more with throwing traditional breaking balls such as sliders and curveballs. This is because pitches that run to the arm-side require pronation at the end of the throw, or the turning of the palm inwards towards the body of the pitcher. These pitchers will struggle with throwing traditional breaking balls and cutters because of the supination that is required. 

Because pronators struggle with throwing more traditional breaking balls, many will turn to the gyro-slider as their go to breaker. The gyro-slider features a more vertical movement pattern, as opposed to the traditional slider that’s coined as being a horizontal movement pattern. This pitch is much easier for a pronator to throw, because it doesn’t require the pitcher to supinate as much at the end of their throw. The pitcher can keep their hand on the top or behind the ball, instead of being on the side or front of the ball– as both of those patterns require a high amount of supination. 

Supinators

Supinators are biased to throwing fastballs that cut, true cutters, and traditional breaking balls. These pitches allow for supinators to be towards the side of the ball when they throw, which is more comfortable for them. Supinators may struggle with throwing sinkers and changeups because of the pronation that’s required for those pitches. Supinators are also more versatile in their arsenal, because they can throw a variety of different off-speed pitches based on their bias. 

Since supinators struggle to throw changeups and sinkers, they may turn to seam-shifted wake to create arm-side movement on these pitches and add variety to their arsenal. Throwing a seam-shifted sinker or changeup allows supinators to throw from a hand position that doesn’t require them to pronate as much. 

Why is this important?

To the average baseball fan this doesn’t matter so much, but if you’re asking yourself why doesn’t this pitcher throw a better slider? The answer is most likely that their genetics or motor-preferences simply don’t allow them to. 

Understanding what makes each pitcher unique makes the game that much more interesting. Sometimes you’ll see a side-arm pitcher throwing a “frisbee” slider that seems unhittable, and other times you’ll see a pitcher throwing straight over the top with a nasty sinker. These differences can give you, as a fan, a clue into the pitcher’s mind and why they throw certain pitches.