Mathieu, normally a cornerback, moved to free safety last week to replace the injured Eric Reid. All he did at his new position was force two fumbles and recover one of them in a 41-17 victory over Arkansas. He also made eight tackles and scored on a 92-yard punt return.
"You have to have confidence in yourself," Mathieu told reporters after the game. "You never want to give up on yourself, and you never want to give up on your team. When you get the chance, you make that big play."
That performance was good enough for Mathieu to replace Claiborne as the No. 1 defensive back in the Rivals.com College Football Power Rankings, which measure the nation's top performers at each position.
Claiborne also had a big game against Arkansas, though he wasn't quite as dominant as Mathieu. Claiborne made three tackles and recorded his fifth interception of the season as the top-ranked Tigers improved to 12-0.
"To be 12-0 right now, it feels amazing," Claiborne said after the game. "This team has worked so hard to get where we are now, and there's no reason to stop."
In the only other change atop the power rankings, Stanford's Andrew Luck regained his status as the nation's No. 1 quarterback after throwing four touchdown passes and one interception in a 28-14 victory over Notre Dame.
Luck set school records Saturday for touchdown passes in a career (80) and a single season (35). John Elway formerly held the record for career touchdowns with 77. Luck's 35 touchdowns this season broke his own record from last season.
"There's no player in America like Andrew Luck," Stanford coach David Shaw told reporters. "There really isn't. Forget about the stats. Forget about the comparisons of other guys or whatever. It doesn't matter. … He doesn't care about stats. He doesn't try to get bigger stats so he can win awards. The kid is the definition of what you would want at the quarterback in all facets."
Luck moved ahead of Baylor's Robert Griffin, who threw a touchdown pass and ran for two more scores in a 66-42 victory over Texas Tech before an apparent concussion prevented him from playing in the second half.
The rankings put a special emphasis on recent performances while also taking career achievements into consideration. Our coordinator rankings exclude coordinators who don't call their own plays or signals.