On Thursday night, the Kansas City Royals meet the New York Yankees for the first time this season, and as SB Nation Kansas City points out, the Royals haven't won a series against the Yankees since 1999. Since 2000, in fact, the Royals hold a miserable 19-56 record against their former ALCS rivals, having been outscored 304 runs to 471.
For a time, these two teams shared one of the very most bitter rivalries of the past fifty years. After falling to the Yankees in the ALCS for three straight seasons (1976-78), the Royals finally gave the business to Reggie Jackson and friends, sweeping them in what was then a five-game series. These teams haven't met in the postseason since (largely because the Royals haven't met anyone in the postseason within the last 24 years), but to Royals fans, at least, the ill will lingered for years.
I probably first became familiar with the concept of baseball in 1987, when I was five years old. Growing up in Kansas City, I naturally became a Royals fan, and even though I was years removed from Yankees playoff drama, everyone taller than me hated the Yankees. Hated them.
As a consequence, I formed the impression that the Royals and Yankees played no one but each other. I knew the Royals by name, but when I saw the Yankees, I saw a mustachioed collective of evil people. I thought the Yankees logo was a mysterious scribble that resembled something terrible (my eventual epiphany of realizing that it was actually an N and a Y was really something), and when I saw someone in a Yankees hat, I assumed that he or she was a bad person for one reason or another.
This rivalry, like many of the ones we're most passionate about, was instilled at an early age. As baseball fans in particular, rivalry narratives are routinely shoved down our throats, but once in a while they provide us with organic motivational sentiment. Where one might otherwise see tonight's game as a mis-match of relatively small consequence, I'll see a battle between two uniforms that once met a lot to me.
Every fan, I'd imagine, can relate to appreciating non-rivalry rivalries like this, and appreciate that the privilege of designating such rivalries doesn't always fall to the people on television.