The International Authority of Baseball & Softball.

Baseball's Umpire Area

The final resource for Baseball's umpires.

Collision Rule

The WBSC is concerned about unnecessary and violent collisions primarily with the catcher at home plate, and with infielders at all bases. The intent of this rule is to encourage base runners and defensive players to avoid such collisions whenever possible.

  1. When there is a collision between a runner and a fielder who clearly is in possession of the ball, or in the act of fielding the ball, the umpire shall judge:
  1. Whether the collision by the runner was avoidable (could the runner have reached the plate without colliding) or unavoidable (the runner’s path to the plate was blocked);
  2. Whether the runner actually was attempting to reach the plate or attempting to dislodge the ball from the fielder; or
  3. Whether the runner was using flagrant contact to maliciously dislodge the ball.


  • If the runner attempted to dislodge the ball, the runner shall be declared out even if the fielder loses possession of the ball. The ball is dead and all other base runners shall return to the last base touched at the time of the interference.
  • If the fielder blocks the path of the base runner to the plate, the runner MAY make contact, slide into, or collide with a fielder as long as the runner is making a legitimate attempt to reach the plate.
  • If the flagrant or malicious contact by the runner was before the runner’s touching the plate, the runner shall be declared out and also ejected from the contest. The ball shall be declared dead immediately. All other base runners shall return to the bases they occupied at the time of the interference.
  • If the contact was after a preceding runner had touched home plate, the preceding runner will be ruled safe, the ball becomes dead immediately and all other base runners will return to the base they had last touched prior to the contact.
  • If the runner is safe and the collision is malicious, the runner shall be ruled safe and ejected from the game
  • If the defensive player blocks the plate or base line clearly without possession of the ball, obstruction shall be called. The umpire shall point and call, “That’s obstruction.” the umpire shall let the play continue until all play has ceased, call time and award any bases that are justified in the Official Rules of Baseball. The obstructed runner is awarded at least one base beyond the base last touched legally before the obstruction.
  • If the base runner collides flagrantly, the runner shall be declared safe on the obstruction, but will be ejected from the contest. The ball is dead.
  • If the runner’s path to the base is blocked and all stipulations above are fulfilled, it is considered unavoidable contact.



OBSTRUCTION is the act of a fielder who, while not in possession of the ball and not in the act of fielding the ball, impedes the progress of any runner.

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Infield Fly

An Infield Fly is a fair fly ball (not including a line drive nor an attempted bunt) which can be caught by an infielder with ordinary effort, when first and second, or first, second and third bases are occupied, before two are out. The pitcher, catcher and any outfielder who stations himself in the infield on the play shall be considered infielders for the purpose of this role.

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A Catch is the act of a fielder in getting secure possession in his hand or glove of a ball in flight and firmly holding it; providing he does not use his cap, protector, pocket or any other part of his uniform in getting possession. It is not a catch, however, if simultaneously or immediately following his contact with the ball, he collides with a player, or with a wall, or if he falls down, as a result of such collision or falling, drops the ball.

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Strike Zone

The Strike Zone is that area over home plate the upper limit of which is a horizontal line at the midpoint between the top of the shoulders and the top of the uniform pants, and the lower level is a line at the hollow beneath the kneecap. The Strike Zone shall be determined from the batter’s stance as the batter is prepared to swing at a pitched ball.

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