Morrison started his professional boxing career on November 10, 1988, with a first-round knockout of William Muhammad in New York City. Three weeks later, he scored another first-round knockout. In 1989, Morrison had 19 wins and no losses, 15 by knockout, in the same year an ,actor Sylvester Stallone, observed one of Morrison's bouts. Stallone arranged a script reading and cast Morrison in the movie "Rocky V" as Tommy "The Machine" Gunn, a young and talented protege of the retired Rocky Balboa. Morrison took a six-month break from boxing to work on the movie in 1990.