In baseball, the pitcher is the player who throws ("pitches") the baseball from the pitcher's mound toward the catcher to begin each play, with the goal of retiring a batter, who attempts to either make contact with the pitched ball or draw a walk. The pitcher is only one out of the many other baseball positions. In the defensive numbering system used in baseball, the pitcher is assigned the number 1. The pitcher is often considered the most important player on the defensive side of the game, and as such is situated at the right end of the defensive spectrum. There are many different types of pitchers, such as the starting pitcher, relief pitcher, middle reliever, lefty specialist, setup man, and the closer.
Traditionally, the pitcher also bats. Starting in 1973 with the American League and spreading to further leagues throughout the 1980s and 1990s, the hitting duties of the pitcher have generally been given over to the position of designated hitter, a cause of some controversy. The National League adopted the designated hitter in 2022; as of 2026, the Japanese Central League is the highest level of competition to not use the designated hitter position.
In most cases, the objective of the pitcher is to deliver the pitch to the catcher without allowing the batter to hit the ball with the bat. A successful pitch is delivered in such a way that the batter either allows the pitch to pass through the strike zone, swings the bat at the ball and misses it, or hits the ball poorly (resulting in a pop fly or ground out). If the batter elects not to swing at the pitch, it is called a strike if any part of the ball passes through the strike zone and a ball when no part of the ball passes through the strike zone. A check swing is when the batter begins to swing, but then stops the swing short. If the batter successfully checks the swing and the pitch is out of the strike zone, it is called a ball.
There are two legal pitching positions, the windup and the set position or stretch. Either position may be used at any time; typically, the windup is used when the bases are empty, while the set position is used when at least one runner is on base. Each position has certain procedures that must be followed. A balk can be called on a pitcher from either position. A power pitcher is one who relies on the velocity of his pitches to succeed. Generally, power pitchers record a high percentage of strikeouts. A control pitcher succeeds by throwing accurate pitches and thus records few walks.
Nearly all action during a game is centered on the pitcher for the defensive team. A pitcher's particular style, time taken between pitches, and skill heavily influence the dynamics of the game and can often determine the victor. Starting with the pivot foot on the pitcher's rubber at the center of the pitcher's mound, which is 60 feet 6 inches (18.44 m) from home plate, the pitcher throws the baseball to the catcher, who is positioned behind home plate and catches the ball. Meanwhile, a batter stands in the batter's box at one side of the plate, and attempts to bat the ball safely into fair play.
The type and sequence of pitches chosen depend upon the particular situation in a game. Because pitchers and catchers must coordinate each pitch, a system of hand signals is used by the catcher to communicate choices to the pitcher, who either vetoes or accepts by shaking his head or nodding. The relationship between pitcher and catcher is so important that some teams select the starting catcher for a particular game based on the starting pitcher. Together, the pitcher and catcher are known as the battery.
Although the object and mechanics of pitching remain the same, pitchers may be classified according to their roles and effectiveness. The starting pitcher begins the game, and he may be followed by various relief pitchers, such as the long reliever, the left-handed specialist, the middle reliever, the setup man, and/or the closer.
In abbreviating baseball positions, P is used as a general designation for pitchers. SP and RP are sometimes used to differentiate starting and relief pitchers, respectively, while LHP and RHP are sometimes used to indicate if a pitcher is left-handed or right-handed, respectively.
In Major League Baseball, baseball rubbing mud is used to condition game balls before pitchers use them.
A skilled pitcher often throws various pitches to prevent the batter from hitting the ball well. The most basic pitch is a fastball, where the pitcher throws the ball as hard as possible. Some pitchers are able to throw a fastball at a speed over 105 miles per hour (169 km/h; 154 ft/s), such as Aroldis Chapman, Ben Joyce, and Jacob Misiorowski. Other common types of pitches are the curveball, slider, changeup, cutter, sinker, screwball, forkball, split-fingered fastball, slurve, knuckleball, and vulcan. These generally are intended to have unusual movement or to deceive the batter as to the rotation or velocity of the ball, making it more difficult to hit. Few pitchers throw all these pitches, but most use a subset or blend of the basic types. Some pitchers release pitches from different arm angles, making it harder for the batter to pick up the ball's flight. (See List of baseball pitches.) A pitcher throwing well on a particular day is said to have brought his "good stuff."
Pitchers use several distinct throwing styles. The most common style is a three-quarters delivery in which the pitcher's arm snaps downward with the ball's release. Some pitchers use a sidearm delivery in which the arm arcs laterally to the torso. Some pitchers use a submarine style in which the pitcher's body tilts sharply downward on delivery, creating an exaggerated sidearm motion in which the pitcher's knuckles come very close to the mound.
Effective pitching is vitally important in baseball. In baseball statistics, for each game, one pitcher will be credited with winning the game, and one pitcher will be charged with losing it. These are not necessarily the starting pitchers for each team; however, a reliever can win, and the starter would then get a no-decision.
Inside pitching is a tactic that involves throwing a pitch close to the batter to make it more difficult to swing their bat, and result in making less solid contact, known as "jamming the hitter." Pitchers with good control are usually more likely to pitch effectively on the inside. It is possible to be effective at disrupting the hitter while also being in the strike zone. When employed correctly, this can result in making a hitter hit pop flies or weak ground balls, and sometimes causes a broken bat. Depending on the exact height, location, and/or type of pitch, it can result in a brushback pitch, or, in the case of a badly controlled pitch, a hit batter. Despite the dangers that it poses to batters, it is a common and legal tactic.
Pitching places significant physical demands on the body, with physiological responses during a game showing heart rate, oxygen consumption, and muscle enzyme changes indicative of moderate to high exercise intensity and potential muscle stress. A full game usually involves 120–170 pitches thrown by each team, and most pitchers begin to tire before they reach this point. As a result, the pitcher who starts a game often will not be the one who finishes it, and he may not be recovered enough to pitch again for a few days. The act of throwing a baseball at high speed is very unnatural to the body and somewhat damaging to human muscles; thus pitchers are very susceptible to injuries, soreness, and general pain.
Baseball teams use two strategies to address this problem: rotation and specialization. To accommodate playing nearly every day, a team will include a group of pitchers who start games and rotate between them, allowing each pitcher to rest for a few days between starts. A team's roster of starting pitchers are usually not even in terms of skill. Exceptional pitchers are highly sought after and in the professional ranks draw large salaries, thus teams can seldom stock each slot in the rotation with top-quality pitchers.