Serie A Wrap: Napoli lose after Rafael howler
The Brazilian was left red-faced after totally misjudging a speculative long-range strike from Achraf Lazaar 14 minutes in to gift the home side the lead.
It was Lazaar's first goal for the club and things went from bad to worse for previously in-form Napoli when Franco Vazquez curled home before half-time after he was set up by Paulo Dybala.
Vazquez then headed down a Dybala cross and Luca Rigoni was on hand to score Palermo's third after 65 minutes to ensure Manolo Gabbiadini's third goal in his last four games late on was merely a consolation.
Defeat for Rafael Benitez's side ended their four-match winning run to ensure they remain four points behind second-placed Roma, while Palermo are up to seventh.
Mohamed Salah marked his first Fiorentina start with a goal and Khouma Babacar struck twice in a 3-1 win at Sassuolo.
Winger Salah joined the Florence club from Chelsea in the deal which took Juan Cuadrado to Stamford Bridge and the Egypt international has wasted no time in making an impact.
Babacar set up the former Basel man for the opening goal after half an hour and Salah returned the favour for the forward two minutes later.
Senegalese forward Babacar added a third goal after 62 minutes and, although Domenico Berardi pulled a goal back five minutes later, Sassuolo were unable to prevent only a second home league defeat of the season.
Victory moves Vincenzo Montella's charges four points behind third-placed Napoli, while Sassuolo sit in 12th.