HOUSTON (Ticker) -- Oklahoma is trying to figure out what happened to its vaunted defense in last week's surprising loss to Oklahoma State.
they prepare for Saturday's Big 12 Conference championship game aaginst No. 12 Colorado, which can become the first team to win back-to-back Big 12 title contests.
It won't be easy for the Buffaloes, who are expected to be without their top two running backs, including Chris Brown, the conference's Player of the Year.
Saturday's contest is a rematch of a regular-season meeting, won by Oklahoma, 27-11, in Norman on November 2.
There will be no national championship implications on the line. Oklahoma State took care of that last week with a 38-28 upset of then fourth-ranked Oklahoma.
Prior to that game, Oklahoma was third in the BCS standings and could have been in position to gain a berth in the Fiesta Bowl if top-ranked Miami were to lose to Virginia Tech this week.
But the Sooners had no answers for Oklahoma State's Josh Fields, who threw four touchdown passes. The Cowboys gained 506 total yards and built a 35-6 lead before Oklahoma made the final respectable.
Sooners co-defensive coordinator Mike Stoops called the performance "embarrassing."
"It's just what I thought," he said. "They just beat us. They outplayed us, outcoached us, executed their plan better than we did."
Now the Sooners turn their attention to Colorado, which will look for another big day from Brian Calhoun.
Calhoun rushed for 167 yards and Brandon Drumm ran for a pair of TDs as the Buffaloes (9-3) tuned up for Saturday's game with a 28-13 victory over the Cornhuskers.
Calhoun and Drumm got plenty of action in place of Brown and Bobby Purify. Brown, a Heisman Trophy candidate, suffered a bruised sternum against Iowa State on November 16 and missed Friday's game with Nebraska.
Brown, who some have compared to Eric Dickerson because of his upright running style, has rushed for 1,744 yards this season. He ranks third in the nation in rushing, averaging 158.5 yards per game.
Purify is doubtful after spraining his ankle against the Cornhuskers. He has rished for 739 yards and three TDs behind Brown this season.
In the first meeting, which began in a heavy rain, Oklahoma converted four Colorado turnovers into 24 points. Brown ran for 103 yards on 25 carries, becoming the first running back to gain 100 yards against Oklahoma since Mississippi's Deuce McAllister in the 1999 Independence Bowl.
Brown had a big game in last year's Big 12 championship game, rushing for 182 yards and three touchdowns in Colorado's 39-37 victory over Texas.
Both teams rely heavily on their running backs as Oklahoma's Quentin Griffin has rushed for 1,522 yards, the eighth-highest total in the nation. Griffin surpassed the century mark in all eight conference games, including 102 yards last week.
The respective quarterbacks, Oklahoma's Nate Hybl and Colorado's Robert Hodge, did not begin the season as starters.
Hybl, the Sooners' starter last year, took over when Jason White suffered a season-ending ACL tear in his right knee in the second game of the season against Alabama. Hodge stepped in when Craig Ochs left school after suffering his third concussion against Southern California on September 21.
Hodge has led the Buffaloes, who started 1-2, to an 8-1 record. Colorado has won three straight since the loss to the Sooners.
Oklahoma is seeking its second Big 12 Conference title in three years. The Sooners defeated Kansas State, 27-24, in 2000 en route to the national championship.