Mann led the NFL in receiving yardage (1,014 yards) and yards per reception (15.4) in 1949. Mann was asked to take a pay cut after the 1949 season and became a "hold out" when the Lions opened practice in July 1950. He was traded to the New York Yankees in August 1950 and released three weeks later. Mann charged that he had been "railroaded" out of professional football for refusing to take a pay cut. He signed with the Green Bay Packers near the end of the 1950 NFL season and was the Packers' leading receiver in 1951. He remained with the Packers through the 1954 season. He was inducted into the Green Bay Packers Hall of Fame in 1988.
Mann later became a lawyer and practiced law in Detroit.