The brawl began in the ninth inning Saturday when Rene Tosoni was hit by a pitch from Mexico's Arnold Leon after Canada's Chris Robinson reached on a bunt single with his team leading 9-3.
The Mexicans considered it a violation of baseball's unwritten rule that you don't run up the score late in a game by bunting to get on base. In Japan, players steal bases and bunt late in games regardless of the score because it's considered fundamentally sound.
Video of the fracas spread across the globe and was a big topic of discussion in Japan, where baseball brawls are rare.
Japan is the defending champion of the World Baseball Classic.