A slider is a breaking ball which typically has higher Speed and less Movement than other breaking balls. Sliders can be very deceptive because they are hard for batters to distinguish from a fastball. Although there is some debate as to whether some pitches break ‘late’ compared to others, the relatively low amount of Movement on sliders may contribute to a late-breaking appearance.

Sliders typically have a Spin Direction that is between 90 and 180 degrees away from the pitcher’s Arm Slot. Around 8:00-10:00 is common for right-handers. They generally have the lowest Spin Efficiency of any pitch type – think 20-70%. Sliders with particularly low Spin Efficiency and high Riflespin (also known as gyro spin) are sometimes called gyro sliders, they may also be described as spinning like a football or a bullet.

Sliders are known for having glove-side Horizontal Movement but may also have some Vertical Movement in either direction. For example, a pitcher with a low Arm Slot may be more prone to positive (upward) Vertical Movement. Sliders with a large amount of Horizontal Movement are sometimes called sweeping sliders.

Sliders can often be effective when thrown down and away from same-handed batters. Alternately they may be effective high and inside, but this location may be less forgiving if the ball isn’t placed as precisely. This is sometimes called a ‘backdoor’ slider. Use the STUFFpL heatmap to see where your slider would perform best.

It’s not unusual for a pitch to blur the line between slider and curveball. This is sometimes referred to as a ‘slurve’ but may be classified as either a slider or curveball according to personal preference.

A curveball is a breaking ball which typically has more Movement than any other pitch type and is thrown at a lower Speed.

Curveballs typically have a Spin Direction that is almost directly across from the pitcher’s Arm Slot. If you have an overhand delivery, this means the Spin Direction will be close to 6:00. Curveballs can have relatively high Spin Efficiency – think 60-100%.

Curveballs are often known for having negative (downward) Vertical Movement, and a curveball that breaks almost straight down is sometimes called a ‘12-6’ curve. If you have a low Arm Slot, your curveball may produce glove-side Horizontal Movement instead. Some pitchers elect to refer to this type of curveball as a slider instead.

Curveballs are often most effective low in the strike zone. Use the STUFFpL heatmap to see where your curveball would perform best.

A knuckle curve is a variation of a curveball that is thrown with the index finger bent so that either the very tip or the first knuckle contacts the ball. Despite the name, a knuckle curve usually has very little in common with a knuckle ball. Although less common, some pitchers have used a pitch that resembles a cross between a knuckle ball and a curveball and referred to it as a knuckle curve.

Some pitchers are able to achieve a lower Spin Direction (closer to 6:00) with a knuckle curve, which may help to emphasize Vertical Movement.