Clarett started at Ohio State for one season, rushing for 1,237 yards (then a school record for a freshman) and scoring 18 touchdowns, which helped the Buckeyes to a 14–0 record and the 2002 BCS National Championship. He scored the winning touchdown against Miami with a five-yard run in the second overtime in the 2003 Fiesta Bowl. He also made a key defensive play in that game, stealing the ball on the Miami 28 from Hurricanes safety Sean Taylor, who was returning an interception from the end zone of a pass thrown by Craig Krenzel. After that play, Ohio State kicked a field goal, giving them a 10-point lead at the time. Clarett was the first freshman to be the leading rusher on a national championship team since Ahman Green of the University of Nebraska–Lincoln in 1995.