If you take a look at the BCS top 20 teams, I believe you will see both Okie State and Mizzou ranked higher than any team we lost to except for OU. We have and do execute at a high level against good opponents. Texas was the worst team in the South and the only team not bowl eliible, but we didn't execute against them. We don't execute consistently. This is the problem.
I'm not buying the hype on OK State or Mizzou. They have exotic, sometimes explosive offenses but are average to poor on defense. Pinkel/Yost can't adjust to defensive pressure, and the Pokes are so terrible on defense that I wouldn't care if they had two Kendall Hunters.
ATM is not a better team than Nebraska, but that was a serious, high-pressure situation and the team basically folded. Championship teams score more than 6 points whether or not the refs are obviously trying to hose them.
Hell, the Texas loss alone should be enough to put this CCG loss into perspective. NU just isn't a great team. They are good, but not great.