Thomas arrived in Hollywood in 1980, and was cast in an episode of CHiPs, which he never filmed, because next day he was set to co-star as Dave Christian, a member on the 1980 gold medal Olympic hockey team in Miracle on Ice, a mini-series. While at Ohio, the head of the theater department, Robert Winters, had sat Duffy down and told him he couldn't be a hockey player and an actor. They both had a good laugh after MOI aired. Duffy made his feature film debut as Nirvana, Charles Bronson's chief nemesis in Death Wish II. He went on to appear in such films as To Live and Die in L.A., The Abyss, Crossroads and State of Grace and guest starred on Night Court, The Fall Guy, The Twilight Zone, MacGyver, and recurred on A Year in the Life on television.