Benitez's contract at the Serie A giants expires at the end of the season and the sanction -- which will see him sit out next Monday's home game with Cesena -- will only fuel speculation that he will not renew his deal.
A statement by Serie A officials on Tuesday said the Spaniard was issued a one-game ban and a fine of 5,000 euros for, "proclaiming in a loud voice while leaving the pitch, 'this shitty Italian football...'."
The incident occurred following Napoli's 2-2 away draw with already relegated Parma, during which Napoli striker Gonzalo Higuain's insults towards Parma goalkeeper Mariano Andujar earned the Argentinian a 10,000 euros fine.
With three games remaining Napoli sit fourth in Italy's top flight, three points behind Lazio in the last possible Champions League qualifying place.
Napoli can however qualify for the Champions League if they win the Europa League. They drew their semi-final first leg with Ukraine outfit Dnipro 1-1, with the second leg scheduled for Thursday.