The New York Yankees rivalry with the Boston Red Sox can be traced all the way back to the mid-1910s. Over 100 years of hatred-filled baseball, no rivalry in the sport is more intense.
We have The Curse the Bambino, The Boston Massacre of 1978, Bucky F**king Dent, Aaron F**king Boone, the most epic comeback in a postseason series the game has ever seen and countless of other events that provoked sheer hatred between each side.
Since the inception of the Wild Card era in 1994, every postseason featured at least one of the two squads for 20 years.