No. 1 Southern California has won 27 straight games and is averaging 51 points per game. And here’s how the Trojans can be beaten Saturday at Notre Dame, with some words of wisdom from former Washington coach Don James, who is taking part in the Master Coaches Survey and has watched all of USC’s games:

1) Be multi-dimensional – USC’s defense is not as good as it was last season. But the Trojans still are quick off the ball, fast getting to it and perfectly capable of taking away what you do best. So you better be able to do multiple things well.

ND’s outlook: The genius of Charlie Weis’ offense is that it really can’t be defined. He wants the Irish to be whatever works best against that day’s opponent.

James’ take: “Charlie’s going to be able to move the ball on them.”

2) It’s not how long, it’s how much – Controlling the ball and keeping Matt Leinart and Co. off the field sounds great in theory. Just as long as those time-consuming drives end in touchdowns. The Trojans scored four TDs in nine plays against Arkansas. They don’t need much time. Figure you need 30 points just to stay in the game, and get them anyway you can. USC’s secondary has been susceptible to long throws.

ND’s outlook: Notre Dame has big receivers (Maurice Stovall and Jeff Samardzija are both 6-foot-5), but they aren’t particularly fast. Brady Quinn throws a decent deep ball.

James’ take: Expand four-down territory. “The points you need are sevens, not threes.”

3) No turnovers – After USC’s 55-19 drubbing of Oklahoma in the Orange Bowl, coach Pete Carroll was asked to define his team. He called the Trojans a “turnover team.” What USC does as well as any team in history is pressure opponents into mistakes and turn them into 28-point quarters.

ND’s outlook: Notre Dame has committed just six turnovers. If that total increases by more than one on Saturday, the Irish are in trouble.

James’ take: “You tell your team turnovers, penalties and kicking game; we can win that against anybody.”

4) Make ’em work – Barring a snow storm, there’s no good way to stop USC’s offense. They’re too good and too diverse. But if you tackle well and stay disciplined, you might be able to limit the long gainers, make the Trojans run eight or 10 plays and hope they get sloppy, which they’ve been at times.

ND’s outlook: Notre Dame ranks 95th in the nation in total defense. And the forecast calls for 66 degrees and sunny Saturday in South Bend, Ind.

James’ take: “Somehow or another you’ve got to contain those two running backs (Reggie Bush and LenDale White). The ones that kill you are those 40-, 50-, 60-yard runs.”

5) Match USC’s poise – The Trojans are as much unflappable as they are unstoppable. When they pulled within 21-17 against Arizona State two weeks ago, USC looked completely in control, and the Sun Devils appeared to be scrambling. Even the crowd seems to get intimidated when the Trojans get rolling.

ND’s outlook: The Irish insist three straight 31-point losses to USC hasn’t left them punchy.

James’ take: “Notre Dame has got to keep their fans in it.”