When the preseason polls were released back in August, USC and Oklahoma stood nos. 1 and 2, respectively, in both the writers’ and coaches’ surveys. Thirteen weekends later, nothing has changed. This Saturday represents the final opportunity for an upset to shake up the rankings and prevent an unbeaten, major-conference team (Auburn in this case) from being denied a shot at the national championship for the first time in the BCS era.

This week, the only shakeup the college football world could provide was the firing of Notre Dame coach Tyrone Willingham after just three seasons. Willingham’s dismissal sets the stage for Utah’s Urban Meyer to take the job and will kick off college football’s silly season, as schools scramble to fill vacancies with high-profile names.

Don’t feel too bad for Willingham; he won’t be unemployed long. He’s rumored to be a top candidate at Washington, and could return to Stanford, where he coached before heading for South Bend. Meanwhile, his firing has touched off debate about the pitiful state of minority hiring in Division I-A, where the number of black head coaches was reduced to two from five in the last month.

Still, there’s plenty of business to be decided on the field Saturday, with two conference championships and a de facto league title game in the ACC, where Virginia Tech visits Miami, with the winner bound for a BCS bowl. All USC needs to do to wrap up its Orange Bowl bid is beat cross-town rival UCLA; Cal will in all likelihood claim a second BCS bid for the Pac-10 if it wins at Southern Miss.

But the real focus will on Kansas City, where BCS no. 2 Oklahoma faces Colorado for the Big XII title, and Atlanta, where the Georgia Dome plays host to BCS no. 3 Auburn and Tennessee in the SEC title match.

AUBURN VS. TENNESSEE (SEC CHAMPIONSHIP)
SATURDAY, 6 P.M. (CBS)

Auburn enters the SEC championship knowing that realistically, it cannot move into the top two spots in the BCS without an Oklahoma or USC loss. Stranger things have happened – in 1998, Kansas State, UCLA, and Tennessee all carried unblemished records into the season’s final Saturday but only Tennessee emerged unscathed.

If Auburn is flat, Tennessee could pull off the upset, but the Vols will have to play much better than they did in a 34-10 loss when the teams faced off in October. The story of that game was turnovers, as Tennessee quarterbacks Erik Ainge and Brent Schaeffer combined to throw five interceptions. Even so, Tennessee would love to have Ainge available for this game, but both he and fellow freshman Schaeffer have been sidelined with injuries. Instead, Rick Clausen, the brother of former Tennessee standout Casey, will make his third straight start.

Tennessee needs tailback Cedric Houston to have some early success to take the pressure off Clausen, but nothing comes easy against an Auburn defense ranked in the top 10 nationally against both the run and the pass. If Tennessee can’t establish the run, Clausen could be in for a miserable day against Rosegreen and his defensive backfield mate, Carlos Rogers.

Auburn isn’t just about defense. On the other side of the ball, the Tigers may be the nation’s most complete team, with a balanced offensive attack led by quarterback Jason Campbell and running backs Ronnie Brown and Carnell “Cadillac” Williams. Tennessee will need to generate a pass rush to contain Campbell, something it has had trouble doing of late.

Tennessee has struggled in its last two games, giving up 64 points in a pair of narrow victories over lightly-regarded Vanderbilt and Kentucky. If Auburn is able to avoid the distractions of the looming BCS disappointment, the game could be a blowout. If the Tigers win and don’t qualify for the Orange Bowl, they will most likely head to the Sugar Bowl to face the winner of the Miami-Virginia Tech game.

OKLAHOMA VS. COLORADO (BIG XII CHAMPIONSHIP)
SATURDAY, 8 P.M. (ABC)

Oklahoma’s lead over Auburn in the computer polls is such that a victory over Colorado by any margin all but guarantees the Sooners a spot in the Orange Bowl. Still, Oklahoma is likely to have plenty of extra motivation coming into this contest, thanks to its awful performance in a 35-7 loss to Kansas State in last year’s Big XII title game.

Oklahoma came into that game as the undisputed no. 1 team in the nation and was being hailed by some as one of the greatest teams of all time. But Kansas State exposed the Sooners’ lack of a rushing attack en route to an easy win. Oklahoma spent the period leading up to the Sugar Bowl defending its spot in the national championship game, but it didn’t make a convincing argument on the field in a loss to LSU.

The Sooners are one-dimensional no longer, thanks to standout freshman running back Adrian Peterson, who has received serious Heisman consideration (no freshman has ever won the award) with 1,671 yards and 12 TDs. Peterson is complemented by last year’s Heisman winner, quarterback Jason White, who may be having a better season with 30 TD passes and just five interceptions. White could become just the second player (Ohio State’s Archie Griffin being the first) to win the Heisman twice. White and Peterson should do well against a Colorado defense ranked 93rd in the nation this season.

Oklahoma has shown some vulnerability against the pass since standout corner Antonio Perkins suffered a knee injury against Texas in early October, but Perkins’s return has sparked a defense that has allowed a total of just three points total in its last two games.

This season has been quite a journey for Colorado, which suffered through a sex-tinged recruiting scandal in the spring. Coach Gary Barnett was put on administrative leave by the school and many assumed he’d be fired, so to see him leading the Buffaloes into the conference championship is a surprise. Nonetheless, Colorado appears overmatched in this game after winning the weak Big XII North with a 7-4 mark. Expect the Sooners to make life miserable for quarterback Joel Klatt all day long and to bottle up running back Bobby Purify on their way to the Orange Bowl.

Mr. Levine writes for FootballOutsiders.com