What's wrong with this defense?

Monte Kiffin said it quietly Saturday, in passing, almost as if it were an established fact.

The 2011 USC Trojans' defense, Kiffin said, is better than the 2010 USC Trojans' defense -- and sizably better, at that. According to Kiffin, a 71-year-old considered a defensive mastermind, his unit was just in the process of finding its way early in this season and on its way to sustained success.

But is it really? Is this defense really all that much better than last year's?

The coaches say yes. But the evidence, in the fallout of Arizona's 41-point performance on Saturday, says no. In 13 games last season, the Trojans gave up 5,200 total yards to their opponents, an average of exactly 400 yards per game. In five games this season, the Trojans have given up 1,898 total yards, an average of roughly 380. Points figures are similar, too.

Last year, USC opponents averaged 26.7 points. This year, they're averaging 26.4 points.

They're simply not doing much better -- if even better at all. Defensive turnover numbers are down and tackles for losses are down, as is the performance in the run game, where teams are finding the Trojans are susceptible in the red zone. The only area noticeably better is tackling, which is shown in USC opponents' average catch yardage. Last year, teams gained 12.1 yards per completion, but that number is down significantly to 10.4 this year.

That can be mostly attributed to tackling in practice. The other thing the USC coaches keep repeating as evidence that the defense is improved is a lack of big plays from opponents, but the truth is that is only a typical indicator of defensive success -- not an end-all-be-all.

Sure, the Trojans didn't give up a single play that went more than 27 yards on Saturday against Arizona. But they gave up 37 first downs, which easily broke the previous opponent record of 32, and 554 total yards of offense.

And that's evidence enough that Kiffin's style wasn't working.

Here is, then, what is wrong with this defense: At the risk of using a Pete Carroll cliche to prove a point, there is a clear lack of competition among the unit that has led to an unstated sort of complacency among some of the starters.

Take this example: last week in practice, the Trojans put freshman Aundrey Walker at right tackle again to challenge Kevin Graf for his starting spot after he played horribly in Tempe.

Graf was upset. But Walker -- and the corresponding serious risk of losing his spot -- motivated him, and he exhibited significant improvement all week in practice and Saturday against the Wildcats.

"It definitely upset me a lot and the coaches knew that," Graf said after the game. "But this week I definitely prepared a lot better and I thought that I knew my opponent a lot better."

Those kinds of moves need to be made on a regular basis at all defensive positions. If DaJohn Harris doesn't have a good game at defensive tackle, George Uko should challenge to start the next week. If Chris Galippo struggles at middle linebacker, Lamar Dawson (if healthy) or Will Andrew should get a chance to unseat him. And the same goes for Jawanza Starling and Demetrius Wright at strong safety.

It has been done occasionally on defense, with Anthony Brown leaping over Tony Burnett for the nickel corner slot and then taking the No. 2 spot when Torin Harris was out because of a shoulder injury.

Backups should be shuffled in back and forth with regularity. More than 46 players should play in a game, and Lane Kiffin, Monte Kiffin and the Trojans should create an atmosphere where players must play physically and with a certain amount of desperation at all times.

That has yet to happen in their 18-game tenure at USC.