Comes from some Ute fans posting on another site that were at the game that some starters were sitting out a series here and there. Also, a poster on that site that is on Utah's staff made a comment a day or two after the game that indeed a few starters took a series or two off, although it was just a passing comment and he didn't elaborate.
Other than that, i am not aware of any other reasons to believe that some players were held out for the game. And I can't prove the claim either - just some people (and someone on Utah's staff) making the claim. I have no reason to think they are lying, but I cannot prove it true neither.
Anyway, if some starters took a series or two off, I don't think it had much affect on the game. I posted just a week or so ago that I think Grimes had an excellent game plan in utilizing the tight ends effectively taking advantage of the way Utah was playing defense and creating mis-matches against the defense. Then again, I am not an expert on football Xs and Os - but just reporting what I observed as I watched the game again last week.