First of all, there's the obvious way. With a 4-1 record and games remaining against the two teams ahead of them, the Cardinal is in the driver's seat. All they have to do is win out, including a win in the Pac-12 Championship game, and they'll be smelling roses.
But that murmur you hear is the voice of reality explaining that the Oregon Ducks are simply too good. That's fine, though, because it fits right along with Plan B.
In this plan the Ducks run the table and finish undefeated at 12-0, which is nice. At the conclusion of the regular season they'd advance to the Pac-12 Championship game, where they'd run roughshod over USC or whichever lamb is sent up from the Pac-12 South to Eugene for the slaughter.