McCann developed a particularly fruitful relationship with the Playwright Brian Friel. He played the role of Gar O'Donnell, the public figure, in a film adaptation of Philadelphia, Here I Come! in 1970 and, despite popular belief, he never played either public or private Gar on stage. He gave a landmark performance as Frank Hardy, the title character, in Faith Healer in 1980 (a role he reprised in 1994), continuing his relationship with Friel through productions of Translations (1988) and Wonderful Tennessee (1993).