Not because Clemson isn't a superior team, because I think they are, but in the first round the Tigers will be facing their first test of the season. We saw what happened to an underprepared Alabama team when battle-hardened LSU came into town. It took Alabama too long to adjust to the superior play of their opponent relative to who they'd played so far.
Utah, coming out fired up and perhaps underestimated, would have its best chance of an upset. It would take a miracle to beat OSU or LSU in the championship game, of course, but they might actually get there under that scenario.