 Born in Rome, Firmani began his career with local A.S. Lodigiani in 1995, moving the following season to Vicenza Calcio.He remained at the latter club for seven years, making his Serie A debut on 26 January 1997 in a 3–2 home win against ACF Fiorentina and going on to collect nearly 100 official appearances.He also scored in the quarter-finals of the 1997–98 UEFA Cup Winners' Cup against Roda JC, in a 9–1 aggregate routing.