Is it too early to talk about the BCS Nightmare Scenarios? Never.
The nightmare that hasn't happened yet is more than two, major conference, undefeated teams. There are still 13 such teams, and at least one in each of the five major conferences. It is also possible that the Big Ten could produce two undefeated teams, since Minnesota and Purdue do not play each other this year.
So, we could have as many as six, major conference, undefeated teams at the end of the season: Miami or Virginia (ACC), Oklahoma, Oklahoma St, or Texas (Big XII), Purdue and Minnesota (Big Ten), Arizona St, Cal, or USC (Pac 10), and Auburn or Georgia (SEC). There are two big matchups this week among this group, Oklahoma-Texas and Cal @ USC.
As an aside, it will be interesting to see how the polls shuffle should one or both of the underdogs win. Does Georgia move up to #1, or does Texas or Cal jump them?
Of course, the biggest nightmare is one of the non-BCS schools crashing the party and pulling $15M out of the big guys' pockets. The leader at the moment is Utah, which is 11th in the polls and 4th in the computers. They still have some upward mobility in the polls, I would think, but I can't imagine them finishing this high in the computers. If they do finish undefeated, they're a lock for a top 12 position and BCS eligibility. Getting to the top six and a guaranteed position may require some help from other teams losing or the generosity of the voters. However, if they do manage to finish undefeated, they may be attractive enough to the Fiesta Bowl that they might invite the Utes whether they are guaranteed a spot or not. That depends on things like what other teams are available, who plays for the title and when the Fiesta gets to pick. It is not likely that Utah would be attractive to the Sugar or Rose Bowls.
Boise St is still climbing as well, though the Broncos will never catch Utah if both stay undefeated. Boise's upside is borderline-top 12. I'm not sure they would be as attractive to one of the BCS bowls as Utah would be.
Southern Miss and Louisville are third and fourth at the moment, but they have the biggest opportunity for advancement. The Golden Eagles already have a win in Lincoln over Nebraska, and still have games to come at Alabama, Memphis and TCU. There is also the season finale with Cal, which was postponed because of Hurricane Ivan.
Louisville's big chance comes October 14th in Miami, when they take on the Hurricanes. A win there, and the Cardinals fly to the head of the line. Louisville and Southern Miss do not face each other this season, so both could finish undefeated.
Navy's undefeated as well, but has one of the most pathetic schedules you could imagine. No shot at the BCS for them.
