The Trojans forced five California turnovers and allowed only one touchdown to bail out the offense on a rare off night as USC won its eighth straight game in the series, 30-9 on Thursday.
''It was huge for us as a confidence booster,'' said linebacker Dion Bailey, who had two interceptions.
''We had to come out and show everybody that we aren't as bad a defense as everybody thinks we are. We held them to only nine points. It was huge today. We picked up our offense. Hopefully next week we're firing on all cylinders and we'll be dangerous.''
That didn't matter because of USC's own opportunistic defense. After allowing 84 points and 946 yards the previous two games, the Trojans kept Cal (3-3, 0-3) off the scoreboard until late in the third quarter and doubled their turnovers caused this season with three interceptions and two fumble recoveries.
''We needed that,'' coach Lane Kiffin said.
''It was much more important for this team to win like that and have a game like that for confidence after all the things our defense has been hearing about them, staff, players, everybody involved. To come out here and get five turnovers and harass the quarterback all game long was really good.''
The main concern for USC was on the health front as the Trojans lost Lee to a right shoulder injury in the first half and leading rusher Marc Tyler to a shoulder injury in the third quarter. Kiffin did not know the extent of the injuries after the game.
Zach Maynard committed four of Cal's five turnovers - surpassing the team's season total coming into the game - and the Bears dropped their sixth straight conference game since late last season. Cal is off to its worst conference start ever under coach Jeff Tedford.
Maynard threw for 294 yards and ran for a touchdown and his half brother, Keenan Allen, had a career-high 13 catches for 160 yards but it wasn't enough to overcome the litany of mistakes.
''You can't beat a good football team like SC when you turn the football over five times, especially down deep in their territory,'' Tedford said.
''There's no question there is some good things, but there are some things that absolutely need to be improved.''
This series has been decidedly one-sided ever since Cal upset USC 34-31 in triple overtime back in 2003. The Trojans have won eight straight and it hasn't even been close of late with USC outscoring Cal 125-29 the last four years.
Cal fell behind 23-0 early in the third quarter before the offense finally got going, with Maynard leading the Bears to a field goal and then scoring on a 3-yard run with 6 seconds left in the third to cut it to 23-9.
But Maynard's third interception midway through the fourth quarter led to Curtis McNeal's 2-yard touchdown run that made it 30-9 with 5:14 remaining.
''They played lights out tonight, no doubt about that,'' Barkley said of his defense.
''They really helped us out on the offensive side of the ball. ... We struggled a little bit on offense, but we protected the ball and they didn't. Ultimately that helped us come out on top.''
It wasn't quite as bad for the Bears as the game a year ago in Los Angeles when USC led 42-0 at halftime. Cal's defense actually did a decent job defending Barkley and the Trojans' high-powered offense, but USC took advantage of short fields for its scores.
Allen fumbled on Cal's fourth play from scrimmage to set the tone for the game, but the Bears withstood that miscue thanks to an odd play call by Kiffin.
On fourth-and-goal from the 8, the Trojans lined up in an off formation and snapped the ball diagonally to Rhett Ellison, who dropped it for a turnover. Kiffin tried the trick play instead of opting for the easy field goal.
''That's no fun,'' Kiffin said. ''You're on ESPN. You have to do something fun.''
The Trojans capitalized on the next turnover as Nick Perry forced a fumble by Maynard that led to Andre Heidari's first field goal.
USC then broke the game open with 17 points in the second quarter, getting a 39-yard TD catch from Lee over fellow freshman Stefan McClure, a field goal after Chris Galippo intercepted Maynard's pass deep in Cal territory and a 7-yard TD pass from Barkley to Carswell after punter Bryan Anger was stopped on a fake that made it 20-0.
Cal's only sustained drive of the half ended in the final minute when Maynard threw into triple coverage and was intercepted in the end zone by Bailey.
''I tried to force the ball on a couple plays,'' Maynard said.
''There's a lot of mental errors. We've got to get better on our check downs and make a better play.''