The Argentina international joined Benfica from River Plate last summer, and he has gone on to register three goals and five assists across 25 appearances.
Fernandez played a key role in Argentina's recent World Cup success, starting five of his country's seven games at the tournament.
As a result of his performances in Qatar, which included one goal and one assist, he received the Young Player of the Tournament award.
Since helping his country lift their third World Cup trophy, the 21-year-old has attracted interest from a number of Europe's biggest clubs.
Chelsea have been leading the pursuit of Fernandez, but they recently failed with a player-plus-cash proposal, which would have comprised an £87m fee as well as three players.
Benfica decided to reject Chelsea's offer, with the Portuguese giants looking to receive Fernandez's £106m release clause in full.
According to the Portuguese newspaper Record, Fernandez has told Benfica's head coach, Roger Schmidt, that he wants to join the Premier League club.
While those conversations reportedly led Benfica president Rui Costa to change his stance and consider a sale, Schmidt has slammed Chelsea's pursuit as "disrespectful."
Although relations between the two clubs have been tested, super-agent Jorge Mendes has travelled to London in an attempt to help the negotiations.
Fernandez, who is under contract until June 2027, played 89 minutes of Benfica's disappointing 3-0 defeat to Braga last weekend.
However, he was left out of the squad for Friday's league meeting with Portimonense due to the uncertainty surrounding his future.
Meanwhile, Chelsea have already experienced a busy transfer window following the recent announcement that Andrey Santos has signed from Brazilian club Vasco da Gama.
Santos becomes Chelsea's third signing of of the window after David Datro Fofana and Benoit Badiashile joined from Molde and Monaco respectively.