SAN FRANCISCO -- The Pac-10 has long been a conference known for its talented quarterbacks and high-powered offenses.

That's what makes the uncertainty at quarterback so many teams are facing at the start of fall practice so unsettling to many teams.

Only Arizona State, Arizona and Washington opened fall practice with returning starters at quarterback entrenched in their jobs.

Everyone else is either breaking in a new starter such as Mark Sanchez at Southern California, challenging a former one like the competition between Nate Longshore and Kevin Riley at California, or hoping a young one will take the job like Nate Costa at Oregon.

``I would say that the team with the experience at quarterback probably has the lead going in because the experience at that position is so important,'' Cal coach Jeff Tedford said. ``When you're breaking in a new quarterback, there's always a growing process.''

USC figures to be an exception to that rule.

The Trojans have done well with first-year starters at quarterback in the past under Pete Carroll, winning a share of the national title with Matt Leinart in 2003 and finishing fourth overall in the country with John David Booty in 2006.

Sanchez has made only three career starts, winning two of them while Booty was hurt last season, and has thrown just seven touchdown passes to six interceptions.

The team best positioned to challenge the Trojans this season could be Arizona State because of the experience of Rudy Carpenter at quarterback.

Carpenter has made 31 straight starts for the Sun Devils, throwing 25 touchdown passes last season to help Arizona State tie the Trojans for the regular season title.

``You can have a guy that's very talented, and there are a lot of them in our league, and a lot of new ones in our league that are going to be playing, but there's nothing like having that experience on the football field,'' Arizona State coach Dennis Erickson said. ``With Rudy coming back, I feel very good about that aspect of it. Not only has he played a lot. He's been very successful.''

Washington coach Tyrone Willingham and Arizona coach Mike Stoops have similar feelings about their own returning starters in Huskies sophomore Jake Locker and Wildcats senior Willie Tuitama.

``You've got to have support people because the quarterback can't do it on their own,'' Oregon coach Mike Bellotti said. ``It's a dogfight and you have to protect your players and be healthy.''

A capsule look at the teams in predicted order of finish:

SOUTHERN CALIFORNIA -- Key players: LB Rey Maualuga, Sr.; FS Taylor Mays, Jr.; RB Joe McKnight, Soph.; DL Fili Moala, Sr. Returning starters: 4 offense, 7 defense.

Notes: Offensive line features four new starters but talented backfield of McKnight, C.J. Gable and Stafon Johnson should make transition easier. ... Strength of the defense is in the back seven, led by Maualuga, Mays, Cushing, and S Kevin Ellison. ... Home game against Ohio State on Sept. 13 highlights nonconference slate and could play big role in determining who makes BCS title game.

ARIZONA STATE -- Key players: QB Rudy Carpenter, Sr.; RB Keegan Herring, Sr.; DE Dexter Davis, Jr.; K-P Thomas Weber, Soph. Returning starters: 7 offense, 7 defense.

Notes: Mike Jones (10 TDs last season) and Chris McGaha (61 catches) lead a talented receiving corps. ... Weber made 24 of 25 field goals as a freshman and won the Lou Groza Award as nation's top kicker. ... A home win over Georgia on Sept. 20 could vault Sun Devils into national title picture.

CALIFORNIA -- Key players: C Alex Mack, Sr.; LB Zach Follett, Sr.; RB Jahvid Best, Soph.; DL Rulon Davis, Sr. Returning starters: 5 offense, 7 defense.

Notes: Expectations are down after Golden Bears lost six of final seven games after having a chance to become No. 1 in the nation last year.

OREGON -- Key players: S Patrick Chung, Sr.; DE Nick Reed, Sr.; C Max Unger, Sr.; RB Jeremiah Johnson, Sr. Returning starters: 6 offense, 7 defense.

Notes: Loss of QB Dennis Dixon and RB Jonathan Stewart leaves big holes on an offense that led conference in scoring.

ARIZONA -- Key players: QB Willie Tuitama, Sr.; TE Rob Gronkowski, Soph.; WR Mike Thomas, Sr.; OT Eben Britton, Jr. Returning starters: 10 offense, 3 defense.

Notes: Coach Mike Stoops has not had a winning season in four years at Tucson and could be on his way out if he can't reverse that trend and lead the Wildcats to their first bowl game in 10 years.

UCLA -- Key players: RB Kahlil Bell, Sr.; K Kai Forbath, Soph.; LB Reggie Carter, Jr. Returning starters: 5 offense, 5 defense.

Notes: Coach Rick Neuheisel returns to the head coaching ranks at his alma mater and brings heralded former USC offensive coordinator Norm Chow with him. ... Ben Olson could be challenged for starting QB job by junior college transfer

OREGON STATE -- Key players: WR Sammie Stroughter, Sr.; CB Brandon Hughes, Sr.; OT Andy Levitre, Sr. Returning starters: 7 offense, 3 defense.

Notes: Beavers have been slow starters and fast finishers in recent years. With road games at Stanford and Penn State to open the schedule, Oregon State will need to be sharp early ... QB Sean Canfield is coming back from a shoulder injury and has fallen behind Lyle Moevao on the depth chart.

WASHINGTON -- Key players: QB Jake Locker, Soph.; LB E.J. Savannah. Jr.; S Mesphin Forrester, Sr. Returning starters: 7 offense, 6 defense.

Notes: The pressure is on coach Tyrone Willingham after posting only 11 wins in his first three seasons. A brutal nonconference schedule that features Oklahoma, BYU and Notre Dame makes Willingham's job even more difficult.

STANFORD -- Key players: WR Richard Sherman, Jr.; LB Clinton Snyder, Jr.; C Alex Fletcher, Sr.; DL Pannel Egboh, Sr. Returning starters: 7 offense, 9 defense.

Notes: Coach Jim Harbaugh tries to build off a debut season highlighted by big wins over USC and Cal. ... Tavita Pritchard, who engineered the win over the Trojans, is competing for starting QB job with Alex Loukas and Jason Forcier.

WASHINGTON STATE -- Key players: WR Brandon Gibson, Sr.; RB Dwight Tardy, Jr.; LB Greg Trent, Sr. Returning starters: 6 offense, 8 defense.

Notes: Coach Paul Wulff has tough task as he tries to make the step up from Eastern Washington. ... Gary Rogers is expected to replace Alex Brink as starting QB.

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AP Sports Writer John Nadel in Los Angeles contributed to this report.