Reasons why ...
I see them winning both Idaho St and Fresno St. They're likely to beat both Wash St and Arizona at home, but I can't see them beating either Oregon or USC at home. Given that, they have to win 2 Pac12 road games or at Michigan to get to 6 wins without slipping up at all with the games I've already thought they'll win. You might point to Colorado as winnable, and I'd agree except I think Colorado's new HC has them trending up and will probably beat the utes at home.
Just can't find 6 wins with that brutal schedule.