Napoli said they will "protect" their rights after players reportedly refused to attend a training retreat.
Club president Aurelio de Laurentiis ordered the team to attend a week-long training camp after slipping 11 points behind league leaders Juventus.
But manager Carlo Ancelotti and his players all returned home following their 1-1 draw with Red Bull Salzburg in the Champions League on Tuesday.
The club did not give details of what sanctions the players may face.
In a statement Napoli said: "The club announces that, with reference to the behaviour of the players on Tuesday, it will proceed to protect its rights on an economic, capital, image and disciplinary levels in every competent jurisdiction.
"It is also made clear that the responsibility to decide on ordering days in a training retreat lies with coach Carlo Ancelotti.
"A press silence has been ordered from now until a date yet to be decided."
A "ritiro" - where the team is confined to a hotel or sometimes the club's own training base - is a common practice in Italian football for sides on a bad run.
The club issued a further statement on Wednesday to clarify that the ritiro was not a punishment for players but a "constructive" move.
Napoli, Serie A runners-up in three of the past four seasons, have won only one of their past five league games and are seventh in the league.