Baseball/Pitcher

Pitchers are by far the most critical players on defense. They are so important on defense that their ability to hit a pitched ball is trivial. When a pitcher falters or tires he is often replaced with a relief pitcher. Pitchers get credit for winning or losing games. A statistic known as earned-run (ERA) average measures the effectiveness of a pitcher, a low ERA generally indicates a good pitcher and a high one indicates a poor one. The pitcher's position in scoring is designated with the number "1"

Pitching

The pitcher spends most of the time when his team is on the field in nearly the center of the infield. He can throw left-handed or right-handed (but he is not allowed to go from pitching left-handed to right-handed or vice versa during the game) and he can throw overhand (the vast majority of pitchers so do), side-arm, or underhand.

Getting outs

A pitcher gets most of his success by inducing outs from batters that he confronts. The outs can result from a strikeout that results from the pitcher getting the batter getting three strikes or hitting a ball so that the batted ball leads to an out (fly balls and line drives caught before landing, ground balls typically to infielders who throw the ball to another base to put out a base runner (usually the batter who must reach first base lest he make an out). If he induces three outs before any runs score, then he has done a good job in that inning.

A pitcher throws a baseball toward the plate, and with that the action usually begins in baseball. The pitcher ordinarily throws the ball toward home plate, where the batter tries either to hit the ball or 'take' a pitch. The batter must swing at a pitched ball that goes through any part of the strike zone lest he get a called strike which may contribute to a strikeout, but if the batter swings and misses at a pitched ball whether it is in or out of the strike zone, then such results in a strike that can also contribute to a strikeout.

The strikeout is ordinarily the least troublesome (but not always the best) result for a pitcher. The batter is out without effectively hitting the ball (except for the rare and unlikely situation in which the batter takes a called third strike or swings and misses but reaches first base when the catcher fails to catch the ball and cannot throw to first base to put out the batter at first base). Pitchers can also get outs (successes against a batter) by inducing the batter to hit a ball so that it either

is caught as a fair or foul fly before it can reach the ground, or
is hit fair to a fielder (typically an infielder, which can include the pitcher or catcher) after hitting the ground who then either touches a base while in possession of the ball before a runner who must reach that base, or throws the ball to another infielder who can touch the base before a base runner obliged to reach that base can touch it. Foul ground balls do not result in outs.

Failure of a pitcher to get an out typically comes from one of four causes:

a hit which results from a batter hitting a fair ball so that it hits the ground before a fielder can retrieve it and throw it to a base so that some infielder can put a base runner out -- or either reaches the fence on the fly or flies over the fence (a ball hit in fair territory but over the fence is the disastrous home run that allows the batter and all base runners then on base to score runs).
a walk in which a batter refuses to swing at four 'balls' (pitches outside the strike zone) before hitting a fair ball or getting a third strike, or (the intentional walk, which is an option in some situations) in which the pitcher deliberately throws a fourth unhittable ball outside the strike zone. The batter is allowed to reach first base, and base runners are compelled to advance as necessary (the batters are usually delighted to advance a base).
a hit batsman, an incident in which a ball striking the batter or his clothing, shoes, or batter's helmet (but not his bat) with a ball not in the strike zone at which the batter does not swing. A ball that hits the batter before striking the batter's bat results in a hit batsman.
an error that allows a batter to reach base safely due to bad fielding by any player (including the pitcher) or allows a baserunner already on base who should be retired on a fielder's choice play.

Pitchers choose the pitches that they use in an effort to confuse a batter typically to induce an out. Such will usually be done with some understanding of the ability of the hitter.

Rules of pitching

The pitcher must not commit a balk while pitching. The pitcher must have contact with the 'rubber' on the pitcher's mound. The rules against the balk practically define how a pitcher can pitch.

With any runners on base -- any base -- a pitcher commits a balk if he:

switches his pitching position from the windup to the set (or vice versa) without properly disengaging the rubber;
while on the rubber, makes a motion associated with his pitch and does not complete the delivery;
when pitching from the set position, fails to make a complete stop with his hands together before beginning to pitch;
throws from the mound to a base without stepping toward (gaining distance in the direction of) that base;
throws or feints a throw from the rubber to an unoccupied base, unless a play is imminent;
steps or feints from the rubber to first or third base without completing the throw (doing so to second base is legal);
delivers a quick return, a pitch thrown right after receiving the ball back, with intent to catch the batter off-guard;
drops the ball while on the rubber, even if by accident, if the ball does not subsequently cross a foul line;
while intentionally walking a batter, releases a pitch while the catcher is out of his box with one or both feet;
unnecessarily delays the game;
pitches while facing away from the batter;
after bringing his hands together on the rubber, separates them except in making a pitch or a throw;
stands on or astride the rubber without the ball, or mimics a pitch without the ball; or throws to first when the first baseman, because of his distance from the base, is unable to make a play on the runner there.
delivers a pitch during a squeeze play or a steal of home, if the catcher or some other player steps on or in front of home base without possession of the ball, or touches the batter or his bat. The ball is dead, the batter is awarded first base, the pitcher is charged with a balk, and the run scores.

Any balk with a runner on base allows each runner to advance one base, including home plate for a runner at third base as the pitcher starts to throw his pitch. Balks are comparatively rare, but they can cause a run to score even ending a game.

Pitchers are never allowed to make deliberate throws at the head or neck of the batter. Umpires have discretion in determining whether a pitcher has deliberately thrown at a batter. In the most flagrant cases an umpire can eject a pitcher for throwing a pitch intended to cause injury to the batter. Accidents happen, and umpires are expected to interpret not-so-deliberate throws as non-violations.

Tampering with the baseball

A pitcher is never allowed to alter a ball in any way by rubbing it against anything (including his clothing and flesh, emery boards, sharp objects) or applying any foreign substance including his own saliva or perspiration which creates a "spitball" that travels erratically. A pitcher caught tampering with the ball will be ejected from the game.

At the discretion of the umpire (typically during cold conditions), umpires will allow pitchers to blow onto their hands so that they can keep their hands nimble enough to pitch effectively.

Pitch types

Pitchers have a variety of pitches available, depending on how they are tossed. A variety of pitches are thrown, and few pitchers are able to use them all effectively. Pitches are known either by their movement (sliders, sinkers, and curves) or by the way they are thrown (screwballs, knuckleballs, and forkballs), or for their speed (fastballs). Pitchers usually vary pitches so that batters can be uncomfortable swinging at the ball. Any pitch can be hit hard and far, usually with a bad result. But some are extremely difficult to hit, especially knuckleballs (which few pitchers throw, but the few who throw them often have long careers) and very fast fastballs.

Some pitches are easily kept in the strike zone so that they will have to be hit to not be strikes; some are more difficult to keep in the strike zone so that if the batter refuses to swing at them he gets a ball. Three strikes (the last either a called or swinging third strike or a foul bunt with two strikes) gets a strikeout, usually the favored out. Four balls, in contrast, allow a batter to reach first base. A pitcher typically tries to avoid hitting the batter with a pitch, which allows the batter to reach first base safely as a hit batsman.

A spitball, an illegal pitch, is infamously difficult to hit but also difficult to get away with over a career.

The easiest pitches to hit are the pitches hard to define -- the 'hanging curve' that does not dip, the slider that does not slide, the sinkerball that does not sink, or a fastball that isn't unusually fast. Pitchers try to avoid throwing such pitches which become many of the hard-hit fly balls and line drives that allow doubles, triples, and home runs.

Attempting to prevent baserunner advances (stolen bases, wild pitches, passed balls)

A pitcher must try to avoid making a wild pitch if runners are on base. Such a pitch goes past the catcher and gives one or more base runners a chance to advance a base. A passed ball or stolen base often results from a pitcher either throwing a pitch far out of the strike zone that the catcher cannot catch or a pitch for which the catcher cannot prepare (such as a low and inside pitch when the catcher expects one high and outside).

A pitcher has some responsibility for deterring the stolen base. To thwart the stolen base a pitcher can pitch efficiently, not giving the base runner an edge in an effort to steal the next pitch.

Typically he pitches so that the pitched ball gets quickly to the catcher who can then make a throw to the base that the base runner is attempting to steal. Of course the pitcher can put a greater effort into inducing an out that might make a stolen base irrelevant. He can throw to an occupied base or to one to which a runner is running.

Fielding

Once the ball is hit, the pitcher is for all practical purposes another infielder. He can catch fair or foul flies (although he usually defers the catch to other infielders or the catcher), and he can retrieve ground balls that he can then throw to bases in efforts to put out base runners. He can usually reach first base before a batter running to first base. On a ball hit to the right side of the infield, a pitcher is usually expected to run to first base, especially if the batter causes the first baseman to go far from first base in an effort to retrieve a ground ball in the knowledge that he must throw to another fielder. In the event of a rundown play he can throw a ball and tag a runner. On what could otherwise be a wild pitch or passed ball he may run to home plate in an effort to retrieve a ball bouncing back or thrown by the catcher to tag a base runner attempting to score.

90% of the game?

It is an old saying that pitching is 90% of the game. Such a claim is terribly imprecise. Runs scored and runs prevented are equally important; offense is just as important as defense.

Pitchers are 'only' about 40% of the 25-man roster. At the low end, teams may have eight pitchers active at one time and at the high end, teams may have eleven. Pitchers are not 90% of the trade value of a team; teams have traded two starting pitchers for one regular position player. The best pitchers do not win 90% of the games that they pitch. No pitcher consistently gets 90% of all batters facing him to make outs.

Most likely, pitching is 90% of the choices on defense. Teams can win or lose because the manager removes a pitcher too late, and a pitcher can win or lose a game in a critical situation through a bad selection of pitches. Teams generally don't get a chance to change a batter's swing during a game.