Robert T. Mathews was an American right-handed professional baseball pitcher who played in the National Association of Professional Base Ball Players, the National League of Major League Baseball and the American Association for twenty years beginning in the late 1860s. He is credited as being one of the inventors of the spitball pitch, in each of three major leagues. which was rediscovered or reintroduced to the major leagues after he died. He is also credited with the first legal pitch which broke away from the batter. He is listed at 5 feet 5 inches tall and 140 pounds, which is small for a pro athlete even in his time, when the average height of an American male in the mid-19th century was 5 foot 7.

In baseball, a complete game (CG) is the act of a pitcher pitching an entire game without the benefit of a relief pitcher. A pitcher who meets this criterion will be credited with a complete game regardless of the number of innings played—pitchers who throw an entire official game that is shortened by rain will still be credited with a complete game, while starting pitchers who are relieved in extra innings after throwing nine or more innings will not be credited with a complete game. A starting pitcher who is replaced by a pinch hitter in the final half inning of a game will still be credited with a complete game.