Why is Jeff Tedford messing around with an offense that's been so successful?

Only one Cal team the past 83 years has averaged more points than any of Tedford's four Cal teams, and two of those teams ranked among the nation's top 10 in scoring.

Apparently, it's not good enough for Tedford because he's relinquishing his play-calling duties and adding a spread offense to the mix this season. If the offense sputters, Tedford will be second-guessed.

Tedford hoped to improve what he has when he hired Mike Dunbar as offensive coordinator and brought in elements of the spread option offense Dunbar ran at Northwestern.

He's also allowing Dunbar to call the plays, something Tedford did the past four seasons. "That's a transition," admitted Tedford, who's been lauded for his play-calling.

Tedford said he imagined from the beginning that someday he might allow someone else to call the plays. Besides, he says, the game plan he and Dunbar devise during the week virtually spells out the play to be called in every situation.

But why add the spread, which includes a shotgun snap Tedford never used, to what the Bears already do well?

Tedford said simply, "It makes us more diverse." But there are several reasons:

• Northwestern was fourth nationally in total offense last year with Dunbar running the show.

• Oregon's offense improved significantly last year when it switched to the spread.

• Tedford wants as many options as possible to combat the varied defenses Cal will see. He might use the spread extensively in some games and not at all in others.

• Tedford likes to present preparation problems for opposing defenses, and adding a completely different package does that.

• With his open-field skills, Marshawn Lynch should benefit from the defensive gaps created by the spread offense. The past three seasons, Noah Herron, Tyrell Sutton and Jason Wright each rushed for more than 1,380 yards at Northwestern, and Lynch is better than any of them.

• Cal was last in the Pac-10 in passing last season, so it can't hurt.

There are potential drawbacks, however:

• The spread works best with a running quarterback and is better suited to the skills of nimble backup Joe Ayoob than starter Nate Longshore, who won't be running the option much, if at all.

• Cal has spent a lot of time working on the spread offense and must hope that preparation does not detract from the successful package Tedford had installed four years ago.

• Having a split personality on offense can upset its rhythm.

The bottom line is Cal has yet to win a Pac-10 championship under Tedford, and he is bold enough to risk changing a successful method in pursuit of a higher goal.