For a clue to the muddled state of quarterbacking in the Pac-10, take a look at Southern California.

Mark Sanchez decided to leave USC after his junior year, and the New York Jets made him the fifth overall pick in last spring's NFL draft.

The Trojans are replacing a first-rounder with a first-timer _ true freshman Matt Barkley. Barkley may turn out to be another in a long line of Trojans stars, but for now he's only first-team All-Potential.

"The big story here is the quarterbacks," USC coach Pete Carroll said Tuesday on the Pac-10 coaches teleconference.

It's a big story from Pullman, Wash., to Tucson, Ariz., and on many campuses it reads like a mystery.

That's quite a change for the Pac-10, where quarterbacks have been as plentiful as sunsets over the Pacific Ocean _ and often as spectacular.

The league has put 13 quarterbacks in the College Football Hall of Fame. Terry Baker, Gary Beban, Jim Plunkett, Carson Palmer and Matt Leinart all won the Heisman Trophy.

But as the 2009 season kicks off, the position is mostly a question.

As in, where have all the QBs gone?

They've gone to the NFL, to the doctor and to the bench.

"I think it's because of a lack of guys coming back," Arizona State coach Dennis Erickson said. "We've had some guys going to the NFL here the last three or four years."

That may change, at least in the near future. ESPN.com recently listed 42 quarterback prospects for the 2010 NFL draft. There was one from Fordham and another from Holy Cross, but none from a Pac-10 school.

Across the conference, the position is so upside-down that the worst team a year ago _ winless Washington _ may have the best quarterback, junior Jake Locker. But while Locker has superb skills, he's returning from an injury and has to adjust to a new scheme under coach Steve Sarkisian.

Only two of the league's top 10 passers from a year ago are starting _ Oregon's Jeremiah Masoli and California's Kevin Riley.

That means many teams will plunge into the season with untested QBs and hope for the best.

USC's Barkley is scheduled to make his second career at No. 6 Ohio State on Sept. 12.

On the same day, UCLA redshirt freshman Kevin Prince will lead the Bruins into Knoxville against Tennessee. Prince beat out Kevin Craft, last year's starter in every game.

At Stanford, redshirt freshman Andrew Luck beat out incumbent Tavita Pritchard and will make his debut at Washington State on Saturday.

"This is their opportunity," Stanford coach Jim Harbaugh said. "In that sense, it is the next wave of guys getting a chance to make a name for themselves and do that within the framework of their particular team. It'll be exciting to watch go down."

The state of Arizona provides two studies of graduation's toll on the position.

Arizona lost Willie Tuitama, the most decorated passer in school history. Neither of his potential replacements _ Matt Scott and Nick Foles _ have emerged in fall camp, and coach Mike Stoops is putting off naming a starter until gametime on Saturday, when the Wildcats open against Central Michigan in Tucson.

Up the road in Tempe, Arizona State senior Danny Sullivan won a competition to succeed Rudy Carpenter, who threw 81 touchdown passes, third in Pac-10 history. But Sullivan may have a tenuous hold on the job; after a recent practice, he suggested that ASU fans might favor untested sophomore Samson Szakacsy or true freshman Brock Osweiler.

"I'm sure they're waiting for Samson or Brock to take me over," Sullivan said. "But I just hope they give me a chance."

The perceived decline at quarterback in the Pac-10 may also be linked to a subtle shift in offenses. The Pac-10 is regarded as a pass-happy league, but the stats told a different story last year.

The Pac-10 placed only one team _ USC, at No. 22 _ in the nation's top 25 passing offenses. By contrast, three Pac-10 teams ranked in the top 25 in rushing offense _ Oregon at No. 2, Stanford at No. 19 and USC, tied for 22nd.

"The productivity in the passing game's not like it used to be," Erickson said. "That's probably the biggest difference. You don't see the (Drew) Bledsoes and Ryan Leafs and guys like that that put up those big numbers because people are running the football a little bit more in this league."

Some quarterbacks are running it more too. Many coaches believe Oregon's Masoli, who rushed for 718 yards and 10 touchdowns last year, is the most dangerous quarterback in the league.

"I think the defenses are more sophisticated and improved and I think the offenses are just different," Oregon offensive coordinator Mark Helfrich said. "There's not as strong of a drop-back passing game that's pervasive, but I think we (the Pac-10) stack up against anybody in terms of production."

One place they don't have to worry about the quarterback is in Corvallis, Ore.

The Oregon State Beavers have two seasoned quarterbacks _ starter Sean Canfield and former No. 1 Lyle Moevao, who is returning from injury. They combined for 3,237 yards and 25 touchdown passes last year.

But coach Mike Riley realizes his advantage may be short-lived, because both Canfield and Moevao are seniors.

"Eventually, and it's always a hard one, you've got to make that transition to a new quarterback," Riley said.

___

AP Sports Writer Anne Peterson in Portland, Ore., contributed to this story.