December 2023, the day before a game, and the manager of a team in Spain’s fourth tier gathers his squad. He reminds them of the plan – the bus will leave at 6am for an 11.30am kick-off 230km away, stopping to pick up players en route – and puts on a video. It includes every goal the opposition’s striker has scored: there are 11 from 13 games and, the centre-back watching soon realises, not one is a tap-in. Instead, Isaac Romero, the Sevilla B forward up there on the screen, makes them all himself. “Unreal, absolutely unreal,” the defender recalls. “You could tell he had to be in the first team, and that’s what happened. He’s on fire.”

That makes it sound easy, but it wasn’t. “I never imagined this,” Isaac says. That morning he played before a few hundred people and didn’t score. The next time he got a goal, there were 12,581 there. The time after that, 13,092. And a week later, when he controlled on his chest, turned, stuck it through the legs of an Osasuna defender and bent a perfect finish into corner, 36,640 people went wild. This Saturday, as he departed after 85 exhausting minutes having barrelled around the pitch and battered Real Sociedad, the Sánchez Pizjuán stood to hand him an ovation and chant the name of their new, unexpected hero.

Things have changed for him, and for them. December would be Isaac’s penultimate game for Sevilla Atlético, the club’s B team. Two days earlier, the first team had been beaten by Mallorca: it was Sevilla’s ninth consecutive game without a win and, a week later, they made it 10 when they were hammered 3-0 by Getafe, slipping to 17th, level on points with 18th. Isaac’s last match for Sevilla Atlético was against El Palo in January. Five days on, he was given a first team debut at Alavés, which was followed immediately by two goals against Getafe in the cup, one against Girona, that belter against Osasuna on his home debut, and the winner against Atlético Madrid. He still couldn’t last 90 minutes, but he had five goals and an assist in his first seven games.

On Saturday he provided another assist as Sevilla defeated Real Sociedad 3-2 and pulled seven points clear of the bottom three, survival nearly secured. The team that could not win in 10 has now just lost once in six – against Real Madrid, when the Isaac volley that might have won it was superbly saved by Andriy Lunin – and, Diario de Sevilla says, the guy most of them hadn’t heard of a month or so ago is the “soul” of the team. He’s also a bit special, a natural finisher with something pure, unrefined about him, a player who says Diego Costa was his idol, crashes into everyone and chases everything, giving “my all until I can’t give any more”. He is, his manager Quique Sánchez Flores insists, an example, the footballer transforming the entire team: “a path for all of them to follow.”

It hasn’t been the most natural, direct path: this isn’t justB team kid makes impact in first team, not least because Isaac is not a kid at all. He’s the footballer’s son with the World Cup winner on his side, 23 but too good for Segunda B.

He couldn’t have foreseen this. Nor could anyone else. If Isaac had had his way this summer, he would probably be playing in the second division; if it had not been for problems with paperwork this winter, the club’s failure to find a forward to fix things, he would probably still be playing in the fourth. This is another case study in overcoming the odds, sure, but also in fortune, good and bad, and football’s ability to somehow find a way.

Romero was born in Lebrija, a town of 27,432 people, 60km (37 miles) south of Seville, where his grandparents had moved in the late 1970s when the marshes alongside the left bank of the Guadalquivir were drained to create arable land and where he still lives. His father, Antonio, had played for Atlético Sanluqueño, reached the second division with Xerez, and became the kit man at local team Atlético Antoniano. His mum, Macarena, runs the bar at the club. And Isaac played for them too, helping them to win promotion from regional andaluza to Spain’s tercera division. This season he played against them in Segunda B. He lost 2-0 and didn’t score. Now he’s scored against Girona and Atlético and been to the Bernabéu.

By the time he helped take Antoniano up, Isaac had been to Sevilla and Cádiz and back. He had joined Sevilla as a kid but departed when they switched to 11-a-side. He spent 18 months at Cádiz, but that didn’t work out either: it was a long way from home. At 19, he was back playing for Antoniano but his coach Francisco José Cordero, who had seen him grow and fill out and had switched him to centre-forward, remained convinced he could make it and called Sevilla. Carlos Marchena, the assistant coach at Sevilla Atlético didn’t just go to see him play; 39 and recently retired, a former World Cup winner who still joined in every session and absolutely loves football, Marchena went and played against him. He laid into Isaac, turning training into a proper test. At the end, he was convinced too.

Coming from regional, amateur football aged 19, Isaac was arriving late, although there was something about his development that made him different. It was 2018 and he joined Sevilla C to start with, progressing to the B team, but he had recurring shoulder problems, suffered a broken leg, and time passed. This summer, he joined the first team in preseason. But José Luis Mendilibar wanted a proven player, a professional. It was not as if Romero could be used occasionally either: because he had turned 23, if he joined the first team, it had to be permanent: he was too old to keep his B team registration and straddle the two sides. So Sevilla signed Mariano Díaz instead. There were no squad slots left.

Isaac was on the verge of leaving permanently – second division Albacete wanted him – only for Sevilla’s sporting director, Victor Orta, to convince him and his father to stay, preaching patience. Yet even when it got to the winter window, with Flores making it very publicly very clear that he no longer had any faith in strikers Mariano or Rafa Mir, who have just five league starts and two goals between them, and the departure of Fernando allowing them to add another player, it didn’t seem likely to be Isaac.

Which is where fortune intervenes. Robert Bozenik’s move from Boavista fell through, even after he had undergone a medical, and then the attempt to get David Datro Fofana, which appeared all done, collapsed because Chelsea had reached their limit for foreign loans. Those weren’t the only deals that couldn’t get done. Mir and Mariano were still around but might as well not have been – “either you reach the level or you don’t play”, Flores said, claiming that “some people interpret demands differently”. Youssef En-Nesyri was at the Africa Cup of Nations, Lucas Ocampos was having to play as a false 9, and the team were in crisis. And so it happened: there were 26 minutes against Alavés, and then the explosion.

A new idol had landed, only he had been there all along.

“We haven’t discovered anyone; we saw the kids in training and we chose, that’s all,” Flores says. “I like Isaac because he does everything you ask of him. He fills us with energy. We’re so lucky he is with us and he’s so humble that it makes him even greater. He’s a lesson in humility for the entire group. It makes you emotional to see young people there. We were young once. The coach opens a door, but they’re the ones that do things; they’re wonderful.”

“He has brought Sevilla hunger; the team needed that and it has proven contagious,” insisted the former manager, Joaquín Caparrós. He is, says Diego Simeone, “everything a coach looks for.” Even the Spain manager, Luis de la Fuente, describes him as “a kid I like a lot”. Everyone does. Life with Isaac is “comfortable” for all of them, En-Nesyri admitted this weekend and for him especially. Liberated by the lad from Lebrija, a partnership between them has built nicely since the Moroccan’s return from Afcon, one headline summing it up simply on Sunday morning: “What a pair of forwards Sevilla have!”

“More than just a good player, Isaac is a good teammate, a good lad, super humble, super hard-working and in the end fortune smiles on people like that,” midfielder Óliver Torres says. “He has waited for his moment: he’s helping us out and hopefully he can keep helping us for a very long time. We’ll be there to hug him every time he scores. The truth is he is a great discovery for everyone.”

Well, almost everyone. Back in December, some defenders already knew: they’d seen Isaac Romero right there on their screens.