I'm a Cards fan too. The supposed Cards-Royals rivalry is because they are in the same state, it doesn't mean they are rivals. The fans in KC are the ones making a big deal out of it. Kansas city, though not a traditional rival, and definitely not on par with the Cubs, is definitely not one-sided, and it's not just about the same state. There's also the World Series history, and the Royals' one shining moment was also something that had played a part in what was one of the longest stretches of no titles for the Cardinals. Obviously that changed in 2006. Add in the fact that there was one specific play that both sides could argue about (even though it didn't determine the series), and there was definitely a back and forth between the fan bases. If this was all one-sided, then you wouldn't have Cardinals fans driving across the state in droves for the series every year. The Mets are not a rival to the Cardinals. In the 80s, when they were in the same division, and were consitently two of the better teams, and often fighting it out at the end, yes, they were rivals. But, since realignment, the Cardinals and Mets have played exactly 12 meaningful games in the last 20 seasons. The Cardinals and Cubs will play 15 meaningful games this season. New York teams, in general, are easy for everyone outside of New York to hate. That doesn't make them a rival. Furthermore, though I have met a Mets fan who once told me in a midtown bar "Yadier Molina broke my heart," I have never met one who talked about the "rivalry" between the two clubs. The claim that the Mets are a bigger rival because they've met in big games is preposterous. I'm guessing you're the same type of fan who thought that the Astros had overtaken the Cubs as the Cardinals' biggest rival in 04-05, too. But that's actually missing the point. At that point, Cards fans only cared about the Astros because they were good. Likewise, in 2006, they only cared about the Mets because they were directly in the way. These, essentially, were "conditional rivalries," and conditional rivalries aren't really rivals. Once the Astros went back to sucking, the games lost the luster. Cards-Cubs games are always big, even if one team sucks, or both do. They could be fighting it out for 5th place in the division, and it'd still be huge to the fans. Anyway, as to the initial question, my guess would be that Cubs fans see the Brewers the way the Cardinals fans saw the Astros, and to some extent see the Brewers: The games are big because they're divisional, and because the other team is currently talented. To some extent, fans might get overly excited because these teams are threatening the "established" powers in the division, and because they have a newly developed, bandwagon hopping fan base. But, they aren't really a rival.