The centre-back, who played in four World Cup matches over the summer, is set to join the Swans On Tuesday for a fee reportedly in the region of £7million.
Fernandez did not appear to be in any doubt over the weekend that his move to the Premier League would go ahead, tweeting his goodbyes to Napoli fans.
“Ciao Napoli. Yes ciao, because it is not goodbye forever! It cannot be, because it is difficult to stay away from a city like this," he wrote.
“A city where I found love and happiness straight away, that gave me so much, which I tried to give back with the best of myself on the field and off.
“A thank you from the heart to this magnificent city, to all its warm inhabitants, thank you to SSC Napoli and its magnificent fans. Thank you to everyone.”
Swansea kicked off their Premier League campaign with a superb 2-1 victory over Manchester United on Saturday. But boss Garry Monk has made no secret of wanting to bring in “two or three” more new signings before the transfer window closes.
Last week he confirmed Fernandez was his first target, saying: “We have had good chats with Fernandez. Fees have been agreed with the clubs and hopefully he’ll be here for medicals this week.
“He brings that pedigree of playing for Napoli and Argentina. He is at a good age for us and will suit Swansea City. We want players who add quality to the squad and he will."