Infield fly rule
The infield fly rule is a baseball rule intended to prevent the defense from getting a "cheap" double play by deliberately dropping a fly ball in the infield. The rule refers mainly to pop-ups, since line drives or weakly hit fly balls that fall to the ground immediately would not allow time for the defense to react fast enough to catch the baserunners off-guard. Because it is applied infrequently and is somewhat technical, the infield fly rule has an exaggerated reputation for being difficult to understand. In popular culture it is portrayed as the sporting world's equivalent to rocket science or brain surgery as an abstruse, technical topic comprehensible only to the select few.
In reality, the infield fly rule is not that complicated. It applies only if the following criteria are met:
- There are less than two out
- First base and second base are occupied or the bases are loaded
- The batter hits a fair fly ball (not a bunt or line drive) catchable by an infielder with ordinary effort. For the purposes of the rule, any fielder, including the pitcher and catcher who is stationed in the general vicinity of the infield counts as an infielder.
If all three criteria are met, the batter is out, whether a fielder catches the ball or not. The only exception is if the ball falls untouched and then bounces into foul territory before passing first or third base, in which case it is a foul ball. Because the batter is out the runners are not forced to advance, though they are permitted to do so at their own risk. As with any other fly ball, the runners must tag before advancing if the ball is caught on the fly and need not tag if it is not caught.
The purpose of the infield fly rule is to prevent the defense from getting a "cheap" double play. In theory, if the rule were not in effect, the runners would be in a no-win situation. If they move away from their starting bases, they are liable to be put out on appeal for not returning to base after a catch. If they stay on or near their bases, the defense could drop the fly deliberately and then record an easy force out double play.
The first version of the rule in which the batter is automatically out dates back to 1894, although it was clarified a number of times since, taking its current form in 1931. In the earlier glove-less days of the game, infielders would attempt to make the double play in such a situation not by letting the ball drop in front of them but by starting to catch it, and then dropping it and picking it up. This led to a first attempt to codify a rule by stating that a ball that was "momentarily held" by the fielder was a catch, negating the intentional drop. This proved to be difficult to enforce, and in addition it left the runners unprotected if the fielder did not touch the ball, so the current version of the rule was eventually the one decided upon.
- Richard Hershberger: "Revisiting the Origins of the Infield Fly Rule", Baseball Research Journal, SABR, Vol. 47, Nr. 2 (Fall 2018), pp. 83-91.