Belotti had started his time with the Sardinian team strongly, scoring two goals in his first three Serie A games.
However, he was forced to leave the pitch before halftime due to the injury.
Cagliari announced that Belotti has suffered an ACL injury in his left knee, which may keep him out for the rest of the season.
The club stated that Belotti underwent diagnostic tests and further examinations will be conducted in the coming days.