Curveball

An animated diagram of a 12–6 curveball

The curveball is a type of pitch in baseball thrown with a characteristic grip and hand movement that imparts forward spin to the ball, causing it to dive in a downward path as it approaches the plate. Varieties of curveballs include the 12-6 curveball and the knuckle curve. Its close relatives are the slider and the slurve. The "curve" of the ball varies from pitcher to pitcher.

Outside the context of baseball, variants of the expression "to throw a curveball" essentially translate to introducing a significant deviation to a preceding concept.

Grip and action

The curveball is gripped much like a cup or drinking glass is held. The pitcher places the middle finger on and parallel to one of the long seams, and the thumb just behind the seam on the opposite side of the ball such that if looking from the top down, the hand should form a "C shape" with the horseshoe pointing in towards the palm following the contour of the thumb. The index finger is placed alongside the middle finger, and the other two extraneous fingers are folded in towards the palm with the knuckle of the ring finger touching the leather. Occasionally some pitchers will flare out these two fingers straight and away from the ball to keep them clear of the throwing motion. The curveball and slider share nearly identical grips and throwing motion.

The delivery of a curveball is entirely different from that of most other pitches. The pitcher at the top of the throwing arc will snap the arm and wrist in a downward motion. The ball first leaves contact with the thumb and tumbles over the index finger thus imparting the forward or "top-spin" characteristic of a curveball. The result is the exact opposite pitch of the four-seam fastball's backspin, but with all four seams rotating in the direction of the flight path with forward-spin, with the axis of rotation perpendicular to the intended flight path much like a reel-type mower or a bowling ball.

The amount of break on the ball depends on how hard the pitcher can snap the throw off, or how much forward spin can be put on the ball. The harder the snap, the more the pitch will break. Curveballs primarily break downwards, but can also break toward the pitcher's off hand to varying degrees. Unlike the fastball, the height of the ball's flight path arc does not necessarily need to occur at the pitcher's release point, and often peaks shortly afterwards. Curveballs are thrown with considerably less velocity than fastballs, because of both the unnatural delivery of the ball and the general rule that pitches thrown with less velocity will break more.[1] A typical curveball in the major collegiate level and above will average between 65 and 80 mph, with the average MLB curve at 77 mph.[2]

From a hitter's perspective, the curveball will start in one location (usually high or at the top of the strike zone) and then dive rapidly as it approaches the plate. The most effective curveballs will start breaking at the height of the arc of the ball flight, and continue to break more and more rapidly as they approach and cross through the strike zone. A curveball that a pitcher fails to put enough spin on will not break much and is colloquially called a "hanging curve". Hanging curves are usually disastrous for a pitcher because the low velocity, non-breaking pitch is left high in the zone where hitters can wait on it and drive it for power.

The curveball is a popular and effective pitch in professional baseball, but it is not particularly widespread in leagues with players younger than college-level players. This is with regard for the safety of the pitcher – not because of its difficulty – though the pitch is widely considered difficult to learn as it requires some degree of mastery and the ability to pinpoint the thrown ball's location. There is generally greater chance of throwing wild pitches when throwing the curveball.

When thrown correctly, it could have a break from seven to as much as 20 inches in comparison to the same pitcher's fastball.[3]

Safety

Due to the unnatural motion required to throw it, the curveball is considered a more advanced pitch and poses inherent risk of injury to a pitcher’s elbow and shoulder. There has been a controversy, as reported in the New York Times, March 12, 2012, about whether curveballs alone are responsible for injuries in young pitchers or whether it is the number of pitches thrown that are the predisposing factor.[4] In theory, allowing time for the cartilage and tendons of the arm to fully develop would protect against injuries. While acquisition of proper form might be protective, Dr. James Andrews is quoted in the article as stating that in many children, insufficient neuromuscular control, lack of proper mechanics, and fatigue make maintenance of proper form unlikely.

The parts of the arm most commonly injured by the curveball are the ligaments in the elbow, the biceps, and the forearm muscles.[5] Major elbow injury requires repair through elbow ligament reconstruction, or Tommy John surgery.

Other Languages
Deutsch: Curveball
français: Balle courbe
한국어: 커브 (야구)
Nederlands: Curveball
svenska: Curveball
中文: 曲球