At international level, he represented Italy on 20 occasions between 1980 and 1983, and was a member of the team that won the 1982 FIFA World Cup.

As a manager, Marini also coached Internazionale, where he won the UEFA Cup in 1994, as well as Como, Cremonese, and the Italy B side.

Throughout his career, he played for several teams, including Fanfulla, Varese, Reggina, Triestina and most notably Internazionale Milano.

[2] Although Marini was not the most elegant or co-ordinated player with his feet from a technical standpoint or in terms of his movements and touch on the ball (leading famous Italian sportswriter Gianni Brera to nickname him "Pinna d'Oro," or golden fin in Italian, a reference to the perceived awkward shape of his feet but also the high quality of his performances), he was an efficient and tenacious player, who was known in particular for his strength, work-rate, tactical intelligence, vision, positioning, and ability to break down plays and subsequently start attacks as a holding midfielder or defensive-minded deep-lying playmaker.

[1][4][5][6][7][8][9][10][11] Beyond his playing ability, he stood out throughout his career for his longevity,[12] as well as his leadership and good sense of humour, which led him to make a name for himself as a key dressing room personality with his clubs.