TUCSON, Ariz. -- Thanks largely to its defense's ability to take the ball away from the opponent, USC is the only Pac-10 team in the national rankings.

The No. 22 Trojans try to legitimize their standing as the best of a mediocre Pac-10 lot when they play at Arizona on Saturday.

USC (3-1, 1-1) lead the nation with a plus-10 turnover margin, and they're hoping that the Wildcats (3-2, 1-1) make some mistakes that play right into the Trojans' hands.

"USC is very impressive in the areas that I admire," Arizona coach Dick Tomey said. "They are leading the nation in turnover margin, and leading the conference in total defense and run defense. Most coaches, if they have their choice, would like to excel in those areas."

USC, led by linebackers Zeke Moreno and Markus Steele, is No. 1 in the Pac-10 in total defense (329.3 yards per game), rushing defense (83.5), pass efficiency defense (100.4) and scoring defense (22.5 points).

The Trojans have not had much trouble making up for the loss of linebacker Chris Claiborne, last season's Pac-10 defensive player of the year.

Arizona's defense, on the other hand, has sorely missed departed all-American cornerback Chris McAlister.

The Trojan defense has recovered 10 fumbles and intercepted seven passes, while its offense has turned the ball over seven times.

Arizona has picked off just one pass and has recovered four fumbles. The Wildcats have turned the ball over eight times.

"We are an attack mode defense," USC coach Paul Hackett said. "We don't want to sit back and wait for the other team to make a mistake. It's the attitude and our speed that has given us a strong feeling of confidence."

They will face an Arizona offense that has been as inconsistent as its two quarterbacks, Keith Smith and Ortege Jenkins. The only consistent threat for the Wildcats has been wide receiver Dennis Northcutt.

Northcutt, who averages 7.2 receptions a game and is fifth nationally in all-purpose yards, has been the steady influence. Of late, the Wildcats have established more of a running game with Trung Canidate having three straight 100-yard plus games.

Both of them are going to be tested by the USC defense.

"When you play somebody as fast as they are, who comes off the edges like they do, rush the passer as well as they do, you have to try to be persistent about the run," Tomey said. "If you go pure pass it will be very hard. It's not going to be easy."

Hackett, who is facing Arizona's flex defense for the first time, has spent extra hours looking at the tapes. The teams have not met since 1996, making the task more difficult.

"It's been interesting to me to look at them for really the first time because I've heard so much about Arizona, and how advanced they are strategically," Hackett said. "It's really exciting to watch them. They play a very distinctive defense. They term it the flex defense. They're running all over the place and it's tough to determine where they'll be, or how you're go about blocking them."

Arizona ranks near the bottom of several key Pac-10 statistical categories. The Wildcats are last in rushing defense (196.2 yards), ninth in scoring defense (33 points) and seventh in total defense (397).

"What's happened to them? I'm not really sure," Hackett said. "They create a lot of problems for the offense. What they do is overload you on the front. They put a ton of people up front and play a form of three-deep, man-to-man defense. They want to get you confused. You're going to get hit for losses in the backfield. Strategically, it's a problem. You either attack it by being super simple, by being basic and fundamental, or you try to exploit it by spreading everyone out and forcing them to do things they don't want to do."

One thing the Wildcats don't want to sees is USC wide receiver R. Jay Soward getting open against a secondary prone to getting beat.

"R. Jay is an electric player," Hackett said. "When the ball is in his hands anything can happen."

For the second week in a row, Mike Van Raaphorst will start at quarterback for the Trojans. Carson Palmer is out indefinitely with a broken collar bone.