A Sampdoria youth product, Ganz started his professional career with the Sampdoria senior side in 1985, making his professional debut in Serie A on 14 September 1986; he won a Coppa Italia with the club in 1988. He later moved to Monza in Serie B during the 1988–89 season, before helping Parma A.C. to Serie A promotion from Serie B during the 1989–90 season. He spent two more seasons in Serie B, and later played for Brescia, finishing the 1991–92 Serie B season as the top goal-scorer, with 19 goals, and helping the club win the league title, earning promotion to Serie A. In the summer of 1992 he transferred to Atalanta, making his Serie A debut with the club, and scoring 14 goals during his first season in the top division. He spent three seasons with the club, although Atalanta were relegated during his second season, and he passed his final season in Serie B.