With City unwilling to match Napoli's valuation of the 29-year-old, the Premier League club could launch a bid to sign Atletico Madrid's Jose Gimenez or Sevilla's Diego Carlos instead, Jamie Jackson of The Guardian reports.
It's understood Napoli are holding out for €80 million (£73.2 million), a figure that is considered much higher than City's estimation, Jackson adds.
Both Carlos and Gimenez have significant release clauses in their contracts, with the Brazilian's set at £109.8 million and the Uruguayan international's at £68.7 million. Manchester City would likely submit an offer significantly lower than the respective clauses, Jackson notes.
City bolstered their defense earlier this summer with the signing of Nathan Ake from Bournemouth for a reported £41-million fee.