After his release from prison in September 1961, Carter became a professional boxer. At , Carter was shorter than the average middleweight, but he fought all of his professional career at 155–160 lb (70–72.6 kg). His aggressive style and punching power (resulting in many early-round knockouts) drew attention, establishing him as a crowd favorite and earning him the nickname "Hurricane". After he defeated a number of middleweight contenders—such as Florentino Fernandez, Holley Mims, Gomeo Brennan, and George Benton—the boxing world took notice. "The Ring" first listed him as one of its "Top 10" middleweight contenders in July 1963. At the end of 1965, they ranked him as the number five middleweight.