A rubber match only refers to the third match when the score is 1-1
"According to Paul Dickson's The New Dickson's Baseball Dictionary (Harcourt Brace, 1999), a "rubber game" is "The last and deciding game of a series when the previous games have been split; e.g., the seventh game of the World Series." This tie-breaking sense of "rubber" apparently originated in the pulse-pounding English game of "bowls," or lawn bowling. Despite its name, bowls has little in common with American bowling, and consists of rolling wooden balls (called "bowls") across a level green, the object being to get your ball as close as possible to (but not to hit) a little white ball at the other end of the green. "Rubber" in its tie-breaking sense first appeared in the context of bowls around 1599, and was in use by the card-playing crowd (whist, bridge, etc.) by 1744. A set of three games of bridge is still generally referred to as a "rubber."
: Unfortunately, no one knows where "rubber" in this sense came from. It appears to be unrelated to the elastic sort of "rubber." (Incidentally, our modern elastic "rubber" is short for "India-rubber," from its original source in the East Indies. "Rubber" previously meant anything used to rub, smooth or clean.) Brewer's Dictionary of Phrase and Fable ventures that the term may have referred to two "bowls" rubbing together, a fatal error in the game of bowls. Or it might be a metaphorical use of "rubber" (something that expunges) referring to the "sudden death" third game of a series, the loss of which would conclusively "rub out" the losing team's hopes. But there is, sad to say, no solid evidence for either theory."