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
Evans' injury was one of a handful for the Sooners defense against Baylor.
Julian Wilson and Aaron Colvin were injured as well.
Sooners defensive coordinator Mike Stoops said more young players could get an opportunity to contribute in the final three games.
"We're getting thinner and thinner," Stoops said. "It's gonna be tough.
"We've got some young guys still who can come on and help us. That's the way it's gonna be. To me, that's just an opportunity for a younger guy. It we're out of the race, then we're out of the race. We've gotta keep getting better for the future, and that's what this program will always be, getting the next guy up."
IKARD, MILLARD ACADEMIC ALL-DISTRICT
Sooners center Gabe Ikard and fullback Trey Millard were named Capitol One Academic All-District for the second consecutive season.
The honorees are chosen by the College Sports Information Directors of America.
The pair was honored in District 7, which includes Colorado, Idaho, Kansas, Montana, Nebraska, New Mexico, Oklahoma, Texas and Wyoming.
Ikard was named a finalist for the 2013 Senior CLASS Award earlier in the week and recently was named one of 16 recipients of the National Football Foundation Scholar-Athlete Award.
Millard suffered a season-ending tear of his anterior cruciate ligament in the win over Texas Tech.