the turning point appears to be when we lost Williams. Our struggles to move the ball and pick up key short yardage 3rd downs basically went away when Williams got injured. There is clearly a big drop off between Williams and Katoa/Soup at running back. Looking back, the injury to Zach was less significant than the injury to Williams.
The run defense is a mess, and it's been that way all year. As we saw vs. USC and Tennesee, our offense was good enough with a top quality running back to overcome and mask some of the defensive shortages. With a more pedestrian offense playing now, it just magnifies the defensive weaknesses.