Mack was a regular on the short-lived PBS series Powerhouse, playing the role of Kevin. His other roles include the villainous John Moesby in the 1987 science fiction film Outerworld, Dr. Darcy in a 1996 episode of Beverly Hills, 90210 (with Ann H. Gillespie and Julie Parrish), Sal the Janitor in the 1996 film Sunset Park, Secret Service Agent Randy in a 2003 episode of The West Wing (also featuring Steven Culp and Billy Mayo), Special Agent Marcus Lemmel in a 2003 episode of The Wire, the "Sophisticated Man" who can't do the Electric Slide in Chris Rock's 2003 film Head of State (featuring Reg E. Cathey and Jude Ciccolella), and Dr. Johnston in HBO's Emmy Award-winning 2004 drama Something the Lord Made (featuring Gabrielle Union). He also had a recurring role on The Young & The Restless