Napoli fans showed their support for Kalidou Koulibaly ahead of the match against Carpi on Sunday after he suffered racial abuse away to Lazio.
Koulibaly was booed, whistled and subjected to discriminatory songs by sections of the Lazio support during a 2-0 win at the Stadio Olimpico on Wednesday, with the referee halting play as a result.
Napoli coach Maurizio Sarri said on Saturday the players had responded by rallying around their team-mate, and fans followed suit at the San Paolo.
Supporters donned masks and held up photographs of the Senegalese centre-back in a stand against racism in football.
Some fans painted their faces, with one such group holding up a sign stating: "It is an honour to be like you".
Serie A fined Lazio EUR50,000 and ordered the Curva Nord be shut for two games as a consequence of the abuse directed at Koulibaly.