Napoli will investigate why Argentina forward Ezequiel Lavezzi arrived back late from international duty on Saturday, the Serie A club said.
"On Monday I will check with the Argentine federation to find out if he lost his passport or not," Napoli president Aurelio De Laurentiis, who already had a fractious relationship with the striker, told reporters.
Coach Walter Mazzarri, who takes charge for the first time in Sunday's home game with Bologna, said his task was difficult enough without Lavezzi's late return from Argentina's World Cup qualifiers.
"He has been careless. Now that he's arrived, we will talk. I don't know how fit he is and if he can play tomorrow," he said.
Mazzarri has replaced Roberto Donadoni, who was sacked earlier this month because of a string of lacklustre displays and supporter discontent over tactics.
Sporting director Pierpaolo Marino was also dismissed but former Italy volleyball coach Gianpaolo Montali has turned down an offer from De Laurentiis to take Marino's place.