In the Official Baseball Rules, the first sentence of Rule 3.03 states, “A player, or players, may be substituted during a game at any time the ball is dead.” It seems obvious to us today that substitutions cannot be made while the ball is in play, but this sentence was not included in the rule book for no reason.
The rule was created after a play by Michael Joseph “King” Kelly, a popular catcher-outfielder in the late-nineteenth century. As Kelly sat on the bench one day in 1891, an opposing batter hit a high foul ball. Kelly quickly recognized that the pop up would be out of the reach of all of his teammates. As a player-manager, Kelly jumped up and went after it, crying out, “Kelly now catching!”
This clever bit of quick thinking allowed Kelly to make the catch, but the umpire refused to call the batter out. Kelly insisted that the play was not against the rules, which at that time stated that substitutions could be made at any time. The rules were changed the following winter to prevent this type of play from ever happening again.