Guys, I hate to break it to you, but we've never been anyone's primary rival.
NU-OU was always bigger to NU than we were. When the Big 12 dictated a change in the NU-OU game, things were different temporarily, but not really, as feelings go. I know that we all bristled at the nub denial that there was any rivalry with us, but even if it was, it was never as big of a deal to them as OU.
I guess CSU has felt like CU is bigger than Wyo as of late, but for the vast majority of their history, their Border War was a much bigger game than their occasional game against us.
As we've noted ad nauseum since we've joined the Pac, even if CU and UU develop a history of close and meaningful games, BYU will always be a bigger rival to them.
There is no one else even on the horizon.
It just is what it is.