teams play every year does not make them rivals. A true sports rivalry is born when there is genuine dislike from the players and fans of both sides towards the other, which usually takes many years if not decades. It may be that down the line Utah and USC develop a rivalry, but for now USC and their fans do not care one lick about Utah. A division rival is simply someone you play every year because you are in the same division. Frankly I don't know why Utah fans are so mad about this. USC is not considered a rival for either of the Arizona schools and they've been in the same conference for almost 50 years. Good for you that you paddled some Trojan bum this weekend but you can't just be like Oprah and hand out unmeaningful rivalries with every team. It just doesn't work like that.
By the same token, BYU will not have immediate rivals in the Big 12. It will take time for that to develop and will probably never develop with most teams. The most likely rivalry for BYU in the Big 12 is TCU given the history but even that isn't certain.
Also, one last note. You can call it the watered down Big 12 all you want but frankly the new Big 12 is better than the PAC and it's not really close. Here is just one metric, average team ranking, but there are many more if you do your research.
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