Infield fly rule

The infield fly rule is a rule of baseball that treats certain fly balls as though caught, before the ball is caught and even if the infielder fails to catch it or drops it on purpose. The umpire's declaration of an infield fly means that the batter is out (and all force plays are removed) regardless of whether the ball is caught. The rule exists to prevent the defense from achieving a double play or triple play by failing to catch a ball that an infielder could catch with ordinary effort. The rule is limited to apply only in situations where this result is possible.

A ball batted into the air subjects baserunners to a dilemma. If the ball is caught, they must return to their original base; if not caught, the batter becomes a runner and certain runners are forced to advance to the next base. Baserunners study the fielder and advance only far enough from the base to ensure that they can return safely. If a presumed catch becomes a non-catch, forced runners must run forward instead of back. This creates an advantage for the defense in intentionally failing to execute an easy catch, which the infield fly rule exists to remove.

Under the Official Baseball Rules used in Major League Baseball and many lower leagues, "Infield Fly" is explained in the definitions of terms: Infield Fly, and rule 5.09 (Batter is out).

The rule applies only when there are fewer than two outs, and there is a force play at third base (i.e., when there are runners at first and second base, or the bases are loaded). In these situations, if a fair fly ball is in play, and in the umpire's judgment is catchable by an infielder with ordinary effort, the umpire shall call "infield fly" (or more often, "infield fly, batter is out") and the batter will be out regardless of whether the ball is actually caught. Umpires typically raise the right arm straight up, index finger pointing up, to signal the rule is in effect.

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