The defender, who joined Napoli from Genk in 2014, is said to be the centre of interest from Barcelona, with the Catalan giants looking for defensive reinforcements.
Jules Kounde was also a potential target for the Blaugrana, but their interest in the Sevilla defender has cooled due to his €70m (£59.4m) price tag.
However, according to Fichajes, Barcelona have turned their attention to Napoli defender Koulibaly, whose current contract expires in the summer of 2023.
Napoli value the centre-back at €35m (£29.7m), but the Blaugrana are keen to lower that price tag by offering Pjanic as part of the deal.
Pjanic is currently on loan at Besiktas, but according to reports he is not in Xavi's plan for next season, with Barcelona keen to offload the 32-year-old in the summer.
Koulibaly has scored three goals in 26 Serie A appearances for Napoli this term, while Pjanic has featured in 20 league games for Besiktas.