When Benfica signed Enzo Fernandez for an initial £8.8m in June it was uncertain whether the River Plate midfielder would join the club immediately or in January.

Chelsea signed Fernandez on transfer deadline day for a record £107m (121m euros) after just half a season in Europe.

The 21-year-old Argentine’s rise has been nothing short of meteoric since returning to River 18 months ago from a loan spell at Defensa y Justicia.

How good has he been this season?

We have heard this story before – a player who was not a household name getting a huge move on the back of a great World Cup.

Fernandez was not even a senior international until a substitute appearance in a friendly against Honduras in September.

His first start for his country did not come until Argentina’s final World Cup group game but he started every game after that. His record in Qatar read one goal, one assist, one World Cup trophy and one young player of the tournament award.

But to call him a World Cup wonder would be a gross simplification of a player who has had a wonderful start to life in Europe.

Wolves were thought to be close to signing Fernandez in the summer but he went to Benfica instead for an initial fee of 10m euros with another 8m in potential add-ons.

Wisely, River kept the rights for 25% of his next transfer fee.

The deal was initially announced in June but it was widely thought Fernandez would only join Benfica after the Copa Libertadores, South America’s Champions League.

If River had gone all the way that would have been the end of October, meaning he would not have moved until January – and so would barely have even played for Benfica yet.

Velez Sarsfield did the Portuguese side a big favour and knocked out River in the last 16 weeks later.

Another few weeks on and he made his Benfica debut, and scored, in a Champions League qualifier against Midtjylland. He netted again in the second leg – and has never looked back.

Fernandez has four goals and seven assists to show from his first 29 games in European football – but that only tells half the story of the box-to-box midfielder’s game.

Only four central midfielders have made more tackles in the Champions League group stages than Fernandez’s 19.

He has made 286 more successful passes than anybody else in the Portuguese top flight this season (1,431 to Nicolas Otamendi’s 1,145).

For Primeira Liga central midfielders he is clear at the top of the list for ball carries, both in number and and distance.

Among players with 1,000 or more minutes in the top six European leagues (England, Spain, Germany, Italy, France and Portugal), only Braga’s Ricardo Horta and Napoli’s Khvicha Kvaratskhelia have been involved in more moves ending with a shot per 90 minutes from open play than Fernandez’s 7.91.

Earlier this month, Portuguese football podcaster Zach Lowy said: “It’s hard to overestimate just how good Fernandez has been for Benfica.

“He really has the complete skillset. He’s been playing in the double pivot with Florentino Luis, who has more of a defensive profile, and he has that mix of a deep-lying playmaker and a box-to-box midfielder.

“The one flaw he has is being a bit rash in his tackles; he can get himself booked early on so he might need to adjust that.”

Fernandez has been shown seven yellow cards in his 29 games and was suspended for their final Champions League group game.

What about before this season?

Fernandez joined River’s academy as a six-year-old, making his debut for the club in 2019.

He spent a year on loan at their top-flight rivals Defensa y Justicia, who were managed by former Chelsea striker Hernan Crespo, playing 32 times and scoring once.

That year saw them win the two biggest trophies in their history – the Copa Sudamericana and Recopa Sudamericana – effectively the South American versions of the Europa League and Super Cup.

He returned to River in the summer of 2021 and left them a year later after 12 goals and 10 assists in 53 games.

Tom Nash, who runs the River Plate in English Twitter account, said: “For River Plate he was class. His form was a huge reason they won the 2021 league title. It was obvious he was a future international by early 2022.”

Even the Buenos Aires club could not have imagined the 25% sell-on deal going this well.

“The fee and timing are a surprise, but his transfer to a regular Champions League contender was expected,” said Nash.

“[A fee of] £60-70m to Liverpool or Chelsea in June was what we imagined, so the rush and outlay from Chelsea is surprising. It feels like they want to pre-empt a battle for him in the summer and are willing to pay that premium to do so.

“River did very well to negotiate a 25% sell-on. That’s why they let him leave for less than the clause last year.

“We were always confident of a £12m+ cut. Benfica’s €120m clause felt more like a deterrent than a negotiation strategy, so we never imagined picking up £28m.”

The timing of the Argentine and Portuguese seasons mean Fernandez has played continually for over a year now.

His wait for a break will surely go on with Chelsea 10th in the Premier League and desperate for their new record signing to push them up the table.

An ‘utterly bonkers’ fee?

Fernandez’s rapid rise and huge fee will undoubtedly come under scrutiny, so will he prove worth the money?

“Enzo Fernandez did not even start in Argentina’s starting XI at the World Cup,” European football journalist James Horncastle told the Euro Leagues podcast. “One of the interesting things is that Argentina used three different midfielders in each of their first three games.

“You have such a small sample size to judge a player. That’s not to say he isn’t a fantastic talent, but to consider paying over 120m euros is still just utterly bonkers.”

However, French journalist Julien Laurens believes the midfielder could eventually become a “game-changer” for Chelsea.

“I still think he can’t quite be a game-changer on his own yet, he needs someone besides him,” he added. “At Benfica he is best in a double-pivot. Enzo is more of a number eight, box-to-box.

“Maybe him on his own might not make that much difference for Chelsea, but if you have the right players around him he could be an amazing signing. If you have that sort of money why not go for it?”