Joe Moorhead underwent surgery to treat an undisclosed, non-COVID related illness, according to a tweet from The Oregonian's John Canzano on Monday.
Moorhead missed the Ducks' game with Stanford, a 31-24 overtime loss for the No. 3 team in the country at that time. Running backs coach and run game coordinator Jim Mastro called the plays in Moorhead's stead.
"Joe Moorhead this morning, non-COVID illness that happened really early this morning, and so he was not available," Mario Cristobal said after the game.
Oregon (4-1, 1-1 Pac-12) is off this week before hosting Cal on Friday, Oct. 15.