Team captain and linebacker Travis Lewis is in charge of choosing each week which defender will wear the No. 12 jersey without the name on the back.
Each week, it rotates to a defender as a tribute to Lewis' close friend and fellow linebacker Austin Box, who died on May 19.
This week, in the biggest rivalry game of Oklahoma's season, Lewis will wear it himself.
"When the guys wear 12, you got to represent it the right way," safety Tony Jefferson told reporters this week. "When you wear the number, you got to really appreciate it. It's not just like you're pulling on any other number. I feel like [Box] is always with us.
"He was a leader, just like Travis is."