Robertson said on Twitter that he had surgery to repair an injury that bothered him last season. The school confirmed the surgery on Sunday and said Robertson will miss the remainder of the season.
Robertson had seven catches for 70 yards and two runs for 40 yards and a touchdown in two games this season. Robertson had 50 catches for 767 yards and seven touchdowns last season as a freshman for the Golden Bears.
Cal (3-2) has lost two straight games following a 3-0 start.