Freshman forward Reeves Nelson suffered a concussion on his first touch of the game, according to Jon Gold of the Los Angeles Daily News.
Nelson said the injury occurred when he and California center Markhuri Sanders-Frison collided early in the first half.
"The doctor said it was a concussion, so I'm going to have to be out for a few days," Nelson said. "I was lying to the trainers just to stay in the game. Obviously, I didn't play as well as I would have liked but I tried to stay in there for the team."
Nelson scored six points on 2-for-5 shooting and grabbed just two rebounds. He had scored a team-high 18 Thursday in UCLA's win over Stanford.
Coach Ben Howland said the team would not practice until Tuesday in preparation for next Sunday's game at USC, but Nelson said he wasn't sure if he'd be ready by then.