Donadoni future at Napoli in doubt
President Aurelio De Laurentiis, who saved the Naples club from extinction and bankrolled their return to the top flight, lambasted Marino's transfer policy before and after Sunday's 2-1 home win over Siena, only their second victory this season.
"Pierpaolo Marino...and the president have decided to mutually end their professional relationship today," a club statement said after Marino met film producer De Laurentiis.
The president was also quoted as criticising former Italy coach Donadoni on Sunday, saying in hindsight he would not have appointed the ex-AC Milan midfielder last March.
Media said Marino's departure increased the likelihood that Donadoni could follow.
Some reports said De Laurentiis had indicated he would make a decision on the coach's future before October 6 while other media quoted De Laurentiis as telling reporters to "leave Donadoni in peace."