Oregon quarterback Marcus Mariota has a partially torn MCL in his left knee, according to television station KVAL in Eugene.
Mariota was wearing a brace over the knee during the Ducks' 26-20 loss to host Stanford on Thursday night.
Mariota, who is a Heisman Trophy contender, completed 20 of 34 passes for 250 yards with two fourth-quarter touchdowns. He acknowledged that his knee was a "little banged up."
He appeared limited in running the ball. He came into the game with 56 rushes for 511 yards but had three carries and was sacked three times for a total of minus-16 rushing yards, including a costly sack and fumble in the second half. Mariota was helped off the field with what looked like a left knee injury but later returned.
"I tend to just not focus on the pain because you've got to play with it," he said after game, when asked how much pain he was in.