Born in
Monza, Italy, Antonioli developed as a player in the youth ranks of
AC Milan. He was later loaned out to
Monza, making his professional debut with the club in 1986, at the age of 16, in a 1–0 defeat to
Juventus in the
Coppa Italia. He also made his Milan debut in the
Coppa Italia, in a 2–1 home win over Lazio, on 3 September 1988, and made his
Serie A debut with the club on 18 April 1992, in a 1–0 win over cross-city rivals
Inter. Due to some promising performances, he was brought to the Milan starting lineup at the beginning of the
1992–93 season, featuring in Milan's 2–1 victory over
Parma in the
1992 Supercoppa Italiana; however, a string of mistakes, including a dreadful fumble in the
Milan derby, which gifted
Luigi de Agostini a soft goal, allowed
Sebastiano Rossi to reclaim his starting spot in goal. Milan won the league title that season, also reaching the
final of the
UEFA Champions League. Antonioli made his final appearance for Milan on 29 November 1992, in 1–0 away win over Juventus, in Serie A, making 27 appearances for the club in total. In 1999, he joined Roma for 10 billion
Italian lire and in
2001, he won a
Scudetto and a
Supercoppa Italiana with
AS Roma, also reaching the final of the
Coppa Italia in 2003. In the summer of 2003, Antonioli joined
Sampdoria on a
free transfer. In
2006–07, with
Luca Castellazzi's emergence between the posts, Antonioli left for former club Bologna on another free transfer. He led Bologna to win Serie A promotion once again in mid-
2008. ==International career==