NORMAN — Most of the adjectives being used this week to describe the Oklahoma defense have one thing in common: They are the exact opposite of those used a month ago.
A defense that during the preseason was certain and stable is uncertain and unstable going into the Sooners' biggest game to date.
"You'd like to be solidified," OU defensive coordinator Brent Venables said.
"In a perfect world, you'd like to have that group of guys. But sometimes, you put another guy in to try to light a fire under somebody to have more urgency to get things right."
Whether he's trying to light a fire or simply getting weaker players off the field, Venables is making changes heading into the third game of the Sooners' season.
Competition is heavy in practice this week at four positions — cornerback, strong safety and both defensive tackle spots.
Junior D.J. Wolfe, an honorable mention all-conference cornerback last season, has been demoted from his starting spot heading into Saturday's game at Oregon.
Venables said he wants to get his best cornerbacks on the field, so Marcus Walker has been added to the competition with Wolfe's backup, Lendy Holmes.
At strong safety, freshman Keenan Clayton was replaced by senior Jason Carter early in last Saturday's 37-20 win over Washington.
That competition will be ongoing in practice this week and could include 230-pound sophomore Nic Harris.
At defensive tackle, Steven Coleman no longer sits atop the depth chart, though all four players in coach Jackie Shipp's rotation — Coleman, Cory Bennett, Carl Pendleton and DeMarcus Granger — played about the same number of snaps.
The interior of the defensive line has been perceived as the weakness of this defense from the day Dusty Dvoracek finished his eligibility.