The No. 7 jersey in football carries a weight. Liverpool have named a stand after Kenny Dalglish, who wore the number with distinction. At Manchester United, Eric Cantona changed the course of the club's history during the 1990s while wearing the shirt number.

It could be argued that the shirt number has an unrivalled significance at Real Madrid. The club's most iconic players have worn the jersey. They include Juanito, whose name is still serenaded during European Cup nights on the seven-minute mark more than a quarter of a century since he died in a car crash, and the club's baby-faced assassins, Emilio Butragueno—who lent his nickname to a famous generation of players, La Quinta del Buitre—and Raul.

And, of course, Cristiano Ronaldo, who surpassed Raul as the club's greatest goalscorer in fewer than half the number of games played, before departing the Spanish capital in the summer for Juventus.

Mariano Diaz steps into the void Ronaldo has left. Real bought him in the offseason from Lyon for a reported fee of €23 million, a figure reduced by 35 per cent because of a buy-back clause Madrid exercised on his rights. 

It is an intimidating mantle for the striker to assume. Many of Madrid's fans were disappointed when club president Florentino Perez didn't make a marquee signing—such as Eden Hazard, who was linked with the club during the summer—to replace Ronaldo. While the memory, too, of Lassana Diarra wearing the storied No. 10 jersey for the club to no great effect is fresh in the memory.

"I don't think wearing No. 7 will be a problem for Mariano," said Raymond Domenech, a former player and manager with Lyon, who also managed France to the final of the 2006 FIFA World Cup. "When I watched him, he's the type of centre-forward who doesn't seem to feel pressure. He always wants the ball. He impressed me by his capacity to fight. He's a fighter. He wasn't afraid to try things. He gives a team spirit. When you have a fighter like that, you follow him. At Lyon, he was an example for that reason.

"For him to take the No. 7 shirt at Real Madrid will be a problem for its supporters because when they will see him dribbling with the ball, it's not Ronaldo. If they compare Mariano to Ronaldo, it will be a problem for [them]."

One of the attributes it appears Mariano shares with Ronaldo is self-belief, which helped him score 18 goals last season for Lyon in Ligue 1. His strike rate was on a par with Mario Balotelli at Nice and Monaco's Radamel Falcao, and it was more than the 13 league goals that Paris Saint-Germain's Kylian Mbappe registered. 

"My understanding is that Mariano wanted the No. 7," said Alex Kirkland, who works as a presenter for Real Madrid TV. "This is not something that has been forced upon him. He had the opportunity to wear the No. 7, and he said, 'Yes, please. I'll take it.' It comes back to the kind of character he is. He's got so much confidence in his own ability.

"It's something that could be a burden for a lot of players, for a different kind of personality, but I don't think he's one of those guys. He's the opposite—he'll relish the chance to wear the No. 7. It's an admirable quality. He's saying, 'I'll take it on—the weight of history that is associated with this number and make it my own.' It's an indication of his strength of character."

Kirkland likens Mariano's explosive playing style—fast, strong and a direct runner—to the Brazilian Ronaldo, while stressing that he's not yet at that calibre.

"He's a matador, a goalscorer," said Pablo Perez, a journalist with El Pais. "The only idea he has between his eyebrows is the idea of scoring a goal. He's a box player. Obviously, if you're a Real Madrid player you have talent, but he's not, say, as skilful as Karim Benzema. If you take him out of the box, he can't play combination football like Benzema, playing wall passes and so on.

"In skill level, he's a rung below Marco Asensio, Isco, Luka Modric, but what Julen Lopetegui wants him for is to score goals. He's the kind of player that helps to unlock a match that is tight."

Mariano is returning home. He joined Real Madrid's youth academy as a teenager in 2011, having grown up in Premia de Mar, a seaside Catalan town less than an hour's drive from the city of Barcelona.

As a kid, he passed a few years at Espanyol's "cantera" (youth academy). He made his mark at Madrid during a dominant season with Castilla, the club's reserve team, when he knocked in 27 goals in 33 games in Spain's Segunda B division in the 2015-16 season. His timing was perfect, as his future at the club was in the balance. 

"He's a player I have been following since he arrived at Real Madrid," Perez said, "and the most surprising thing about his career was the moment he renewed his contract with the club in January 2016. The previous season with Castilla (2014-15), it didn't look like he'd stay at the club. It's a fact the club didn't rate him. He was around 22 years old, and he wasn't part of the plans for Real Madrid. In his head, he wasn't set to continue in Madrid or thinking about playing in the first team.

"That summer of 2015, Rafa Benitez, as manager, had highlighted in red the name of Borja Mayoral, as a possible striker for the first team. Then Mariano goes out and scores a record number of goals for Castilla that season—27. After spending two weeks over the Christmas holidays racked by doubts, wondering if he'd find a club in the first division, he got a phone call from the club in January 2016. They gave him a contract to renew for five years. It was his first big contract. It changed his career."

Mariano was sold to Lyon in the summer of 2017, having only managed to get limited first-team chances during Zinedine Zidane's reign as Real Madrid manager. At Lyon, he flourished as part of a young, exciting attacking trident with Memphis Depay and Nabil Fekir.

At the back of Mariano's mind, however, were always thoughts of a possible return to Real Madrid, says Kirkland. 

"Having come up through the youth ranks at Real Madrid, and having broken into the first-team squad, and then having left the club and gone to Lyon, a lot of players might have thought: 'OK—I had my time at Real Madrid. Maybe I didn't quite make the grade. I'm going to pursue my career elsewhere.' But he was consistent in saying, 'No, no. I'm not done at Real Madrid. My goal is to play well enough that the club exercise the option to bring me back. I'm going to impress them enough to make that happen,'" notes Kirkland. 

"Over the summer when there were reports in the media saying that Mariano had turned down the chance to return to Real Madrid, he tweeted (in Spanish): 'You don't say, "No" to Real Madrid.' He was quite single-minded in his determination to earn the right to come back." 

Now is his time. He is 25 years of age. He's not old, but neither is he young anymore. Inter Milan's Mauro Icardi, for instance, is the same age as Mariano, and he has already been top scorer in Serie A—twice. Depay, his former strike partner at Lyon, is a year younger than Mariano but has already clocked up 39 international appearances for the Netherlands. Mariano has yet to be capped for Spain (although he has one cap for the Dominican Republic, his mother's country).

"The age of 25 is not old, but it is the end of 'the young player,'" Domenech said. "When you're 25, you're no longer a young player. You are a player. It's different when you're 22, 23 or 24. We can't say: 'one day, he will be a good player.' Mariano has to be a good player now. We can't think of him being a great player in three or four years' time."

Mariano must seize his chance—when he gets it. Kirkland says Mariano will get his chances, as did previous back-up strikers such as Chicharito and Alvaro Morata, who both scored important goals for the club. It is a long season, and Madrid has battles on several fronts, including the FIFA Club World Cup. 

Mariano has to take his place in the pecking order behind first-choice players Gareth Bale, Benzema and Asensio. Vinicius Jr., who scored again for Castilla at the weekend and is in Madrid's UEFA Champions League squad for the season, is also hovering in the wings.

"I think he will only play five minutes here, 10 minutes there, and probably the games in Spain's cup competition, the Copa del Rey," Domenech said, "but when you see the kind of players who are playing in Real Madrid, it will be really difficult for him to play."

It is true, but it looks as if Mariano will make the most of those brief chances. He made a big statement in Madrid's opening match of their defence of the Champions League against AS Roma on Wednesday. He came off the bench—in his first start under Lopetegui—by scoring a scintillating goal in stoppage time.

It was a goal worthy of Ronaldo and the other great No. 7s in Real Madrid's history. 

Follow Richard on Twitter: @Richard_Fitz