Marc Stocco Explains How Pitchers Use the Seams on the Baseball to Their Advantage

Marc Stocco of Surrey, BC, is a starting pitcher for his university team and fell in love with pitching because of all the ways that he could throw the ball. However, pitching is not simple. Baseball design makes batting against a skilled pitcher highly unpredictable. In turn, pitchers gain those skills by using baseball seams to control their throws.

Using Baseball Seams for Pitching Grip

Most young pitchers begin by learning the four-seam fastball grip. This grip offers the straightest throw and as such, all fielders learn the grip to some degree. It is the most efficient and fastest pitch, notes Marc Stocco.

The seams help pitchers place their fingers correctly. For example, in the two-seam fastball, the pitch moves their fingers from crossing the horseshoe to gripping the parallel seams at their closest point. This grip gives the pitcher more control to add motion or change the speed of the pitch.

Adding fingers to a pitch adds more resistance and slows the speed of the pitch. Some pitchers add further resistance by bringing their index finger and thumb together into a circle.

Curveballs and sliders are the classic breaking ball pitches. Finger positions change on the seams to increase directional spin.

Most pitchers experiment with their own grip alterations to achieve maximum control and motion. The seams on the ball nearly always establish that pitcher’s frame of reference for gripping the ball just right.

Marc Stocco Explains How Batters Perceive a Pitch Based on Seam Movement

In major league baseball, batters train to observe how the seams move in the air in an effort to anticipate the ball’s position on the plate. This skill is very difficult to acquire, particularly as pitching speeds increase.

Furthermore, pitchers can use this to their advantage, says Marc Stocco. For example, batters often assume that the spinning sideways horseshoe (seam motion) is a fastball. The lack of arc in the ball confirms this. If the pitcher uses a change-up, the seam motion remains the same, but the speed of the pitch decreases significantly. As a result, the batter swings early. This scenario is a classic technique pitchers use to keep batters guessing.

Baseball Seams and Aerodynamics

Baseball would be far less interesting if the ball itself were completely smooth. Instead, the seams provide a unique air resistance that gives pitchers options. Depending on the creativity, knowledge, and skill of each player, pitching becomes more potent.

Using the grips listed above, pitchers can experiment with different speeds and throwing techniques to find their sweet spot. What most skilled pitchers are looking for is intentional motion. Among pitching coaches, this motion is often viewed from behind the plate and represented in clock-hand position to identify the amount of three-dimensional arc.

For example, a curve ball with a 10–3 arc means that the batter watched the ball move from 10 o’clock to 3 o’clock before crossing the plate. The greater the arc, the greater the “breaking” in the curve, slider, sinker, etc. And the lesser the arc, the more likelihood that the pitch is either a fastball or change-up.

How this motion works is due in large part to how the pitcher grips and throws the ball. However, notes Marc Stocco, without the wind resistance on the seams, this motion would be nearly impossible. Baseball seams provide resistance (high air pressure on the top of the ball, low air pressure on the bottom) allowing pitchers to manipulate the ball’s movement on its way to the plate.

Student Athlete, Baseball Player