Ronald Jones II felt the cold and the altitude when USC played at Colorado last week.
The sophomore tailback, who gained a freshman record 177 yards the week before against Arizona, carried the ball 19 times for 61 yards. It was the Texas native's fewest since the Trojans' fourth game.
"I think I let the situation get to me a little bit, which is something I can't do at this level," he said Wednesday. "I can't make excuses. I could have performed better overall."
Jones intends to get back on track Saturday when USC plays Oregon at Autzen Stadium in Eugene, Ore.