The Argentina midfielder has joined the big-spending Premier League side in a mega-money £107million move from Benfica - little more than six months after joining the Portuguese side for just £15million. The 22-year-old has put pen-to-paper on an eight-year contract at Stamford Bridge, tying him to the Blues until 2031.
Fernandez's move makes him Chelsea's club record purchase, breaking the record previously held by Romelu Lukaku, and is both a British transfer record and a Premier League transfer record. It is also Benfica's record sale and, bizarrely, River Plate's record sale, as the Argentine club still held 25 percent of his economic rights following his 2022 move, earning them a cool £26.75million.
The transfer was not finalised ahead of Tuesday night's transfer deadline. Chelsea subsequently submitted a deal sheet and asked for an extension to complete the paperwork on the move, with Fernandez having already undergone his medical in Lisbon.
With all parties subsequently satisfied, the deal has now been ratified and signed off, giving the Blues their No.1 January target.
Much of Tuesday's negotiations settled around how Chelsea would pay for the Argentina midfielder, whom they have been pushing to sign since the World Cup. Benfica, who have made a reputation of being difficult to deal with, especially when transfer windows are heading towards their close, refused to go below the release clause in his contract, despite Fernandez making clear his desire to move to the Premier League as soon as possible.
Chelsea couldn't spend the entire £107m in one go, otherwise, allied to their other spending, it would destroy their Financial Fair Play workarounds. But after going back and forth over initial payments and instalment plans throughout the day, a deal was eventually reached that sees the Blues pay £30million up front, followed by five further payments of £15.4million.
While negotiations were ongoing, Benfica left Fernandez out of their squad to face Arouca on Tuesday night, a game they won 3-0. Speaking afterwards, coach Roger Schmidt said: "It's always difficult to lose a good player in the winter market, but today we showed that we are a good team without him, that we are capable of playing good football without him, that the players are focused on getting the most points, to be champions.
"Benfica is much bigger than a player. We just need players who are happy to play for Benfica, who are passionate. We had a player who wanted to leave and a club willing to pay the clause, we couldn't do anything. We accepted and looked into it."
Fernandez played 29 times in all competitions for Benfica, scoring four goals and grabbing seven assists.
Chelsea spent over £300million during the transfer window, as the club's new ownership group, led by Todd Boehly and Clearlake Capital, pressed ahead in their quest to overhaul the current squad.
Monaco defender Benoit Badiashile, Molde striker David Datro Fofana, Mykhaylo Mudryk, who arrived in a deal worth up to £87m from Shakhtar Donetsk, PSV Eindhoven winger Noni Madueke. and young Brazilian midfielder Andrey Santos all arrived on permanent deals. Joao Felix joined on loan from Atletico Madrid while a deal was also thrashed out that will see Lyon's Malo Gusto join the club, although he is remaining in France until the summer.
The Blues also recruited heavily during the summer transfer window too - the club's first since Roman Abramovich's exit as owner - with Kalidou Koulibaly, Raheem Sterling, Wesley Fofana, Marc Cucerella, Pierre-Emerick Aubameyang and Carney Chukwuemeka.
All told, the new ownership group's total outlay on transfers stands at approximately £550million across the past two transfer windows, but on the field they have struggled this term, sitting 10th in the Premier League table, 10 points adrift of the top four, ahead of Friday night's meeting with local rivals Fulham.