There are always a lot of moving parts when it comes to defense. This is, of course, also true on the offensive side of the ball. The difference, however, is that a player on defense even taking the slightest incorrect angle can directly lead to six points for the other team. Whereas on offense, mistakes can be a little more forgiving, and it can be easier for someone else to make up for an error in the moment.
In order for USC to perform at the level that is needed there, the Trojans will have to show the ability to work cohesively.