Baer's defense in 2002 was an experienced, veteran crew, who could basically coach themselves. A lot of times, you would see the defensive captains making some pretty smart audibles, despite Baer's play call.
If you look at Kent Baer's playcalling, he got away with a lot of bad calls in the beginning of the year, because of the caliber of the defense.
I would actually argue, that our defense could have done a decent job against that USC team. While it wouldn't have been enough to win it (there was no doubting the outcome, our offense was completely inept for most of the game), making better calls on defense would have at least slowed down Carson Palmer and co. Instead, Chow and Palmer had a field day during that second half, picking off our defensive secondary single coverage all day long. All it took were a few minor adjustments on Chow's part, and they steamrolled us.
Losing a lot of those players in 2003 then revealed the ineptitude of Kent Baer. No longer was his "stack the box with 8 and single cover every receiver" working, even against the teams weaker than a USC. There was still a good bit of defensive talent there, but he couldn't coach them up properly during the off-season.
He still didn't learn in 2004.