Cagliari president Massimo Cellino confirmed the decision Sunday night, shortly after a 1-3 loss at home to Roma, reports Xinhua.
The Sardinian club has lost four of their past five matches and won just three times since the start of 2014.
Cellino was reportedly on the verge of firing Lopez in February, but instead dismissed Pulga as assistant coach.
Pulga was in charge of Cagliari in the 2012-13 season, with Lopez as his assistant, before the duo swapped roles in July.
Lopez’s dismissal is the 14th coaching change in Serie A this season.