Freshman linebacker Jordan Evans injured his ankle on a kickoff near the end of the first half of Oklahoma's 41-12 loss to Baylor on Thursday.
A source close to Evans said Evans could miss Saturday's game against Iowa State but should be back in action soon.
Evans is the latest in a string of linebacker injuries for the Sooners.
Corey Nelson was lost for the season with a torn pectoral muscle suffered against TCU and Frank Shannon has suffered multiple injuries this season, though he has started every game.
The Sooners weren't good on third down against Baylor, converting just 4 of 17.
But the reality is even more disturbing for Oklahoma.
The Sooners had nine opportunities on third and four yards or less and converted just two.
"We were horrible in third and short, fourth and short, goal line," Sooners coach Bob Stoops said. "They out executed us, definitely. You've got to make those. You're not gonna come in here and have one touchdown in the middle of the third quarter and think you're gonna win. It's just not gonna happen."
The Sooners averaged just 1.7 yards with third and four or less. That averaged was exactly half of the Sooners' overall yards per play in the game.
DEFENSE COULD GET EVEN YOUNGER