Right now, the Utah game is just the next game they have to win as they control their destiny getting to the conference championship game and ultimately the playoffs.
If BYU had the same record as Utah, for example, and a conference championship was out of reach - at that point you can focus on the importance of winning the rivalry game for the sake of it being a rivalry.
But BYU has bigger hopes right now than just beating Utah on Saturday - and they have to win on Saturday to keep moving towards that goal.
So sure - talk about the rivalry. Talk about how Utah will be up for the game regardless of their season being meaningless at this point. But they won't be playing hard because it's a rivalry. They'll be playing hard for everything else.