Utes win the PAC 12 south if they win against either Washington or Colorado. (This assuming they beat ASU and Oregon as well.) The scenarios don’t look good if they lose both of those games. My best guess is Utah loses to Washington, then meets Colorado when both programs are 6-2 (Colorado loses to UCLA or WSU). Winner of that game takes the South.
USC will be out with a third loss at Washington.
Prediction: Utah vs Washington in the PAC12 Champ game.