A highly talented yet humble player, throughout his career, Antonelli played for Italian clubs Monza, Vicenza, A.C. Milan, Genoa, and Roma. He contributed to Milan's tenth league title victory during the 1978–79 Serie A season with 21 appearances and 5 goals; following Milan's relegation after their involvement in the Totonero 1980 match-fixing scandal, he remained with the club and played a decisive role in helping the team win the Serie B title in 1981 and earn promotion to Serie A, scoring 15 goals, and finishing the season as the top scorer in Serie B.