— When Oklahoma boarded the bus in Fort Worth, Texas, on Saturday, it believed it was heading to the Sugar Bowl.

By Sunday night, it was making plans to face No. 10 Texas A&M in the Cotton Bowl.

What changed for the Sooners? Nothing that was in their control.

The Sooners (10-2, 8-1 Big 12) are the Big 12 co-champions along with Kansas State. The Wildcats earned the Big 12’s automatic BCS berth to the Fiesta Bowl because of their 24-19 win over the Sooners on Sept. 22.

OU believed it would receive an at-large bid to the Sugar Bowl because it was ranked No. 11 in the BCS standings.

That spot, however, evaporated when MAC champion Northern Illinois jumped seven spots to No. 15 in the BCS standings in the final week.

BCS conference champions — the winners of the ACC, Big East, Big Ten, Big 12, Pac-12 and SEC — are guaranteed spots in one of the four BCS bowl games: Fiesta, Orange, Rose and Sugar.

If one of the other conference champions is ranked in the top 12 of the final BCS Standings — or in the top 16 while also being ranked above a BCS conference champion — that program is ensured an automatic berth.

Big Ten champion Wisconsin is still outside the BCS standings. Big East winner Louisville is No. 21.

There it is.

Northern Illinois, which didn’t make an appearance in the BCS standings until Nov. 25, is in. OU is out.

The Sooners were not complaining on Sunday about falling to the Cotton Bowl.

“Our players are enthusiastic about winning another Big 12 championship and look forward to competing against Texas A&M in the AT&T Cotton Bowl Classic,” OU coach Bob Stoops said in statement. “The Cotton Bowl has long been a marquee postseason destination, and we’re excited about being selected to play there a second time. Cowboys Stadium is a great venue, and I know Sooner fans will be excited to make the trip to support us.”

The game, which kicks off at 7 p.m. Jan. 4 at Cowboys Stadium in Arlington, Texas, will pit the Sooners against the Aggies for the first time in the postseason. It will also be Texas A&M’s first meeting with a Big 12 team since it left the league for the SEC over the summer.

The Cotton Bowl was thrilled with the teams it received.

“We hit a home run today,” Tommy Bain, Chairman of the AT&T Cotton Bowl Classic said in a statement. “When our Team Selection Committee met for the first time a few weeks ago, we circled this matchup as the one we most wanted, and the cards fell in our favor today.”

OU beat Arkansas, 10-3, to cap the 2001 season in its first Cotton Bowl appearance.

The Aggies are making their first appearance in the AT&T Cotton Bowl as a member of the SEC. Texas A&M last appeared in the game in 2011, losing to LSU, 41-24.

“Our football team is excited to play another game against a storied program such as Oklahoma,” Texas A&M coach Kevin Sumlin said in statement. “We have been led all year by a great group of seniors and to be rewarded with a great experience like the Cotton Bowl is something they will cherish. Plenty of their family and friends will be able to watch them play as well, and the hospitality is second to none.”

Sumlin, who was an assistant coach at OU from 2004-07, will face the Sooners for the first time.

It’s a great matchup, but one the Sooners or few others didn’t see materializing until the components of the BCS formula started coming out Sunday afternoon.

Several losses on Friday night and Saturday night opened the door for the Huskies and slammed it shut on the Sooners.

Northern Illinois beat Kent State, which was No. 17 in the BCS standings, on Friday. Also, UCLA, which had been No. 16 in the standings, lost to Stanford in the Pac-12 title game

The last piece of the puzzle was Nebraska, which had been No. 12 in the BCS standings, getting demolished by Wisconsin in the Big Ten championship game Saturday.

Nebraska finished 16th in the BCS standings. UCLA was No. 17.

The Oklahoma State Cowboys finished the regular season 7-5, and will play in the Heart of Dallas Bowl on New Year's Day against Purdue.

Oklahoma State and Purdue have not played each other since 1997, when the two teams met in the Alamo Bowl, which was won 33-20 by Purdue.

The Boilermakers finished 2012 6-6 and fired their coach after the season.