It’s a big game for Trojans -- and Pete Carroll

The Pacific 10 Conference football championship is on the line.

A shot at the Bowl Championship Series title game also could be in play.

So USC’s game on Saturday at Oregon is huge for the Trojans.

For Pete Carroll as well.

While USC’s coach is far more beloved than embattled, there are rumblings among Trojans fans aching for a trip to a postseason game at the Rose Bowl that is not considered a consolation prize.

Few regular-season games in Carroll’s eight-plus seasons have put him on the spot as he will be on Halloween night at Autzen Stadium.

In case you missed it, Carroll is 0 for 3 in his last three trips to the Beaver State.

The Trojans are a one-loss team instead of unbeaten one because of questionable coaching decisions before and during their defeat at Washington.

And, as of late, USC’s defense has been a second-half mess.

All of that, of course, ultimately comes back to Carroll, a defense-minded coach who has long been regarded as a master of motivation and halftime adjustments, characteristics that helped the Trojans win seven consecutive Pac-10 titles and make seven straight BCS bowl game appearances.

One or both of those streaks could end if the Trojans again go south in the Pacific Northwest.

Carroll’s troubles in Oregon began in 2006 when USC fell behind Oregon State at Corvallis. The Trojans staged a late comeback but came up short when the Beavers batted away John David Booty’s two-point conversion pass.

In 2007, Oregon quarterback Dennis Dixon sliced and diced the Trojans’ defense, while Trojans quarterback Mark Sanchez struggled in his third career start.

Last season, Oregon State blew USC’s defense off the line of scrimmage en route to victory over the then-No. 1 Trojans.

Conceivably, USC could have been top-ranked in the polls going into Saturday’s game at Eugene had Carroll not mishandled the Trojans’ quarterback situation before the Pac-10 opener at Washington last month.

Previous USC quarterbacks readying for first starts under Carroll were managed masterfully before and during their debuts.

In 2003, Carroll and former offensive coordinator Norm Chow built up Matt Leinart’s confidence and then protected him with a game plan that played to his strengths at Auburn.

Carroll and former offensive coordinators Steve Sarkisian and Lane Kiffin did the same for Booty at Arkansas in 2006.

Carroll and Sarkisian propped up Sanchez and treated him with kid gloves when he started in place of Booty against Arizona in 2007. And Carroll and first-year quarterbacks coach Jeremy Bates put reassuring hands on the precocious Barkley’s shoulders before this season’s opener against San Jose State.

The formula worked. Everyone came out a winner.

But with Barkley ailing from a bone bruise suffered against Ohio State, Carroll apparently could not bring himself to afford Aaron Corp the same treatment.

Hoping that Barkley would somehow overcome his injury in the eleventh hour to play at Washington, neither Carroll nor Bates officially told Corp, or the teammates that might be called on to rally around him, that the sophomore would start for the first time.

On game day, Corp took the field without Carroll’s signature confidence boost or a game plan that played to his mobility. The result: a poor performance by Corp and a 16-13 loss to Sarkisian’s unranked Huskies.

Barkley returned to the lineup the next week and has continued to show that he is capable of becoming one of the top quarterbacks in college football.

But would he have done so without Carroll’s help?

While Barkley is growing and managing an offense that appears to be finding its stride, Carroll now must fix a defense that is reeling.

Notre Dame quarterback Jimmy Clausen pushed the Trojans to the brink in the second half at South Bend, Ind.

If it wasn’t already official, Oregon State Coach Mike Riley last week officially replaced California’s Jeff Tedford as Carroll’s personal nemesis by orchestrating an offense that was one step ahead of Carroll’s defensive calls throughout the second half at the Coliseum.

USC won both games. But after giving up no more than six points in the second half of each of their first five games, the Trojans surrendered 20 against Notre Dame and 27 against Oregon State.

Now comes 10th-ranked Oregon, which has rebounded from its season-opening loss against Boise State to average 34 points a game and leads the Pac-10 with a 4-0 mark.

A USC loss ends all hope of the Trojans playing for the BCS title on Jan. 7 at the Rose Bowl. The traditional Rose Bowl on New Year’s Day also becomes a longshot, consolation prize or not.

With their team threatening to end USC’s Pac-10 dominance, Oregon’s famously zealous fans are expected to be at their best before and after kickoff.

The Trojans, and especially Carroll, need to be the same.

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gary.klein@latimes.com

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