OU Head Coach Bob Stoops said that Corey Nelson will move into Lewis' position and that Tony Jefferson will work at the nickel back. Javon Harris will then see increased time at safety.
"We're disappointed for Travis," Stoops said. "He has worked very hard and I know he'll want to get back as quickly as possible.
"We'll adapt in the meantime. We've recruited very well and have some excellent athletes in those positions. I'm confident that those players will perform well."
OU Head Athletic Trainer Scott Anderson said the injury does not require surgery. He said that the treatment consists of rest and immobilization.
Lewis, a senior from San Antonio, Texas, has 362 tackles through his first three seasons at Oklahoma along with eight interceptions and six sacks.
Nelson, a sophomore from Dallas, saw action in all 14 games last season accumulating 21 tackles.