It's the same in french football (soccer) where Olympique de Marseille is always the team who draw the biggest total of supporter in his away game and could be considered rivals by more than one team while it's a normal game for the club.
thats not rivalry in my eyes, thats the fact of a big brand. If your team looses against Bayern München, Olympic Marseille, Real madrid, barcelona the fans normally ain't mad. A rivalry is something Like Dortmund and Schalke, where your fans judge a season like hey we got relegated but we beat Dortmund. Those game have special meaning for both fan group, and you normally shouldn't go with the wrong jersey in a fan pub(something you could do with a Bayern München jersey, when you ain't going in a 1860 München fan pub).