In 2008, USC produced one of the all-time great college defenses. It took just two years for the unit to become mediocre-to-bad.
Last fall, the Trojans surrendered 44 plays of 20 or more yards, which ranked 102nd in the nation. By comparison, the 2008 unit yielded just 14, the lowest total over the past three years by six.
So what happened?
Well, for one, Pete Carroll, who'd built one of the nation's premier defensive powers, bolted for the Seattle Seahawks. Next: The talent he left behind for new coach Lane Kiffin wasn't nearly as good as it had been from 2002-2008. Then Kiffin, worried about injuries, significantly limited tackling during preseason camp. Finally, it seemed that the Trojans never fully figured out new coordinator Monte Kiffin's Tampa-2 scheme, which had been so successful in the NFL.
The result? A unit that surrendered a Pac-10-high 30 TD passes (five more than ninth-place Washington State) and wasn't much better against the run, ranking sixth in the conference (140.5).
But if you're wondering why many still rate the Trojans as the favorites in the Pac-12 South Division and believe they will improve upon their 8-5 finish of a year ago, the defense is a good place to start.
"I feel like we know what we're doing a little bit better as far as it being the second year in the system," Lane Kiffin said. "And in scrimmage formats, we're tackling better."
That will be put to its first test Saturday when Minnesota comes calling to the Coliseum.
The Trojans welcome back seven starters from last year's unit. They look strong at end with Nick Perry, Devon Kennard and Wes Horton. And few teams boast a better safety-cornerback combination than All-American T.J. McDonald and Nickell Robey. But there are questions at linebacker, where they will be young around injury-prone Chris Galippo.
The Golden Gophers shouldn't provide too difficult a test. Coming off a 3-9 season in which Tim Brewster got fired and was replaced by Jerry Kill, who rebuilt Northern Illinois, they are replacing three starters on their offensive line and they don't look like a team that will be throwing the ball well. They are, however, intriguing at quarterback. That's where MarQueis Gray steps in. He's a 6-foot-4, 240-pound junior who has been primarily a receiver, though he got behind center in "Wildcat" formations. Passing the ball over the past two years, he's just 8-of-23 for 86 yards with a TD and an interception.
Of course, Kiffin went the "oh, no" route and compared him to former Texas quarterback Vince Young.
"It's very scary for us," he said. "We've got our hands full. This is a big-time challenge for our defense."
USC won at Minnesota 32-21 last year, a victory that was part of a 4-0 start. But the Trojans proved inconsistent on both sides of the ball once conference play began, inspiring some questions of motivation because NCAA sanctions made them ineligible for the postseason. That's an issue again this fall, though it's probably not one in the season-opener, when everyone is fired up to play.
"I don't think the motivation shows up as much early in the year," Kiffin said. "It becomes more of an issue towards the end of the year or if you hit one or two losses in a row there."
Still, with Matt Barkley at quarterback and a strong crew of receivers, the Trojans should at least be a factor in determining other team's postseasons. As for the South Division, that probably hangs on how much the Trojans' defense reverts back to its old ways. Preseason optimism about knowing the scheme better and improved tackling only goes so far.
Said Kiffin: "That all sounds good but it won't mean anything if come Saturday we don't do it when it really counts."