Firrito had a career best year in 2007. He was the main defender for the Roos, with his bulky yet small frame attracting the big forwards of the game. After Glenn Archer's retirement, Archer handed over his no. 11 guernsey to Firrito, who wore the number instead of the no. 24 he had worn since his debut in 2004. He has played over 200 AFL matches and all for North Melbourne Football Club.
Michael Firrito was selected by Mick Malthouse for 2008 International Rules series for Australia against Ireland. In the first Test, Firrito played as full back and right corner back before replacing Nathan Bock as goalkeeper for the second test, when he made many good saves despite conceding 4 goals. Firrito was one of 5 North Melbourne players selected in the squad, along with Daniel Wells, Drew Petrie, Brent Harvey and Matt Campbell