 By that time, the sport as played in Canada had diverged markedly from its rugby origins with the introduction of the Burnside rules, and started to become more similar to the American game.For much of the early part of the 20th century, the game was contested by intraprovincial leagues, or unions.In 1907, several of the stronger senior clubs in Ontario and Quebec formed the Interprovincial Rugby Football Union (IRFU or Big Four).