Final answer:
Julius Erving is the only player voted MVP in both the ABA and the NBA.
Step-by-step explanation:
The only player who has been voted Most Valuable Player (MVP) in both the American Basketball Association (ABA) and the National Basketball Association (NBA) is Julius Erving, also known as Dr. J. Erving won the MVP award in the ABA in 1974 and 1976 while playing for the New York Nets. After the merger between the ABA and NBA, Erving went on to win the NBA MVP award in 1981 as a member of the Philadelphia 76ers.