2010 and BYU has dominated them statistically in every game except on the scoreboard. Which shows that BYU didn't struggle mentally against Utah.
No the real reason is a lot more simple than what most people think and that is having a lack of a decent game plan. Last year for example BYU had 2 weeks to prepare after Whit said what the Utah defensive game plan was and yet Bronco and BYU only had practice for 5 days during that entire 2 week period and none of which was geared towards defeating Whit's and Utah's defensive game plan. It is as if Bronco doesn't care whether he wins or loses the rivalry game.