Marini was born in Lodi. Nicknamed "Malik" by fans, he played 256 matches in Serie A, scoring 10 goals. Throughout his career, he played for several teams, including Fanfulla, Varese, Reggina, Triestina and most notably Internazionale Milano. With Inter, he won a Serie A title ("Scudetto") during the 1979–80 season, and two Coppa Italia titles in 1978 and 1982.