Lopez replaced Pulga in the hot seat July 2013, with the latter dropping down to the role of assistant, but was dismissed after Sunday's 3-1 defeat to Roma.
Pulga was released by the club in February, but now looks set to make a return to the dugout.
"I have sacked Lopez as coach of Cagliari and brought back Pulga," president Cellino is quoted as saying by ANSA.
"It’s an act that I wanted to avoid, but Lopez has forced me into this position, and I am not one to hide."
Cagliari sit 15th in Serie A, seven points clear of the relegation zone.
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