“Today is a day to talk about my boys,” the Leganés coach Borja Jiménez said. About Miguel de la Fuente, the striker that played two months with a torn meniscus, and Renato Tapia, the Peru captain who missed the Copa América because he had no team and no insurance. About Yvan Neyou, the midfielder who faced two Simeones in one day and didn’t know, unaware that Giuliano was Diego’s son because “I don’t watch much football”. About Munir El Haddadi, who’s scored for a record seven La Liga clubs. And about the rest of them: Dani Raba, Diego García and Javi Hernandez, who was once at the best club on earth and on Sunday played for the team his captain says “will never be forgotten now”.

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It was a day to talk about Matija Nastasic and Óscar Rodríguez, Jorge Sáenz and Darko Brasanac, the whole Leganés side, even if most people were talking about the team they beat. About Seydouba Cissé, who grew up in Guinea sharing boots with his best mate, a half each played barefoot, and whose dad told him to be a teacher because this would never be a career; the kid who cried at the embassy gates, waited three months for the papers to get to Spain and three years to see his mum again once he had. Whose then-agent, Ilaix Moriba’s dad, told him he had a team in Madrid and for one, brief moment he thought about that team, only for it to be this one instead, and who is happy about that now. And how could he not be?

Because on Sunday night Adri Altimira, brought up at La Masia, nephew of the head of the academy where he couldn’t take the final step, was back to face the senior side for the first time, via Croatia and north Africa. And to beat them too, Leganés winning 1-0 at Barcelona. With all these boys and Marko Dmitrovic too, the 6ft 3in, 14-stone, no-nonsense Serbian that some drunken madman actually thought he could fight, the goalkeeper who once scored a penalty and once missed one too, and now stood in Barcelona’s way but still reckoned the save everyone raved about wasn’t all that. With Sergio González, the captain with the business studies degree, a masters in sports law and a PhD in doing it the hard way.

Released by Real Madrid at youth level, González played in Las Rozas, Villaviciosa de Odón, Alcorcón and San Sebastián de los Reyes, his career looking like he had hopped in his car and was just driving round the M40, the capital’s 61km orbital, pulling off at the next exit and signing for the nearest club. Along the way, a fourth-tier footballer, he was told he wasn’t good enough for Segunda B, Spain’s 80-team, four-group, regionalised third tier, wasn’t good enough for the second division and certainly wasn’t good enough for the first. “I’ve lived with prejudices and it hurts,” he told El País’s Diego Torres. “You can reach the top quickly, through a big club’s academy, a call from some higher club, or you can get there a longer route through bashing your head. I got there bashing my head.”

Why stop now? González’s journey round the motorway brought him to his fifth Madrid satellite town, the biggest of them all: a city with streets named after Scorpions and AC/DC and a team that could aspire to the first division. They could with him there, anyway. So this summer, aged 32, a player whose level of on-field concentration makes your head hurt let alone his, González finally made it to the top flight. Which doesn’t stop him attending conferences and continuing to study; in fact, he says academia is good for him, providing a mental release, and the evidence suggests he’s right. The defender whose goal at Ponferradina had effectively saved Leganés from being relegated to the third tier – known as “the well” because it’s easy enough to fall into and almost impossible to climb out of – and helped San Sebastián to leave behind tercera, Mirandes to escape segunda B, also led Leganés back to primera after five years away, returning as champions of the second division. And then on Sunday night he scored the goal that defeated Barcelona.

There were three minutes gone when Óscar went to take a corner. They had been working on it all week – the movement, the screens put in front of Barcelona’s players, the delivery – and it was perfect. “When I saw the ball in the air, I thought: ‘This is a goal, 100%,’” González said. Another bash of the head and the ball was flying past Iñaki Peña and into the net. There were still 86 minutes to go. “We said to each other that it was too soon,” Gonzalez said. “Like we’re in a position to choose when we score!”

Robert Lewandowski could have scored a hat-trick, one effort from four yards somehow blocked by Dmitrovic. Jules Koundé had two chances. And Raphinha guided a superb shot, on the bounce and the turn, towards the top corner. But Dmitrovic brilliantly reached that and stopped a handful more – even if he insisted afterwards that one stop made against Lewandowski, in behind the defence, was more bad miss than great save and he had gone the wrong way. And although Leganés had lived on the edge to start with, ultimately they kept Barcelona at arm’s length. “I felt more under pressure first half. The second went by fast; it felt under control,” Jiménez said.

Asked if he would have settled for a draw when a goal up at half-time, Jiménez insisted: “No, that would have been for losers.” This was a game they could win, and all the more so now. Three days earlier, the club’s owner, Jeff Luhnow, had spoken at the club’s Christmas dinner. “Why couldn’t we win there?” he had asked. “Las Palmas have beaten Barcelona and we have beaten Las Palmas, so …” Barcelona were not in a good place, it was true: they were top, sure, but they had only won one of their last five league games, dropping 10 of 15 points. And so it was, on the weekend that Madrid’s other clubs reopened the title race.

On Saturday night, Rayo Vallecano had gone 2-0 up, 3-2 down and finally drawn 3-3 with Real Madrid, a 4-3 win evading them with the last kick. On Sunday at 2pm – that slot when you don’t know whether it’s time for the Vermouth aperitif, lunch or straight to the gin and tonics, according to AS – Getafe took Atlético Madrid to the line but eventually lost to a Alexander Sørloth header. And on Sunday night Leganés defeated Barcelona. It had seemed done after the clásico but six games and just five points later, while Barcelona are still top, they’re level with Atlético and only one point ahead of Madrid, having played a game more than both. “We have given a little life to the title race,” Jiménez said. They had given themselves a little life too.

When he was little, growing up in Avila, Jiménez collected toy cars, cutting pictures out of magazines and sticking them on to pieces of cardboard. His family were driving instructors and that was what he was expected to do too. Instead, he became a football manager. At 39, he’s the second youngest coach in primera after Iñigo Pérez, making his debut season in the top flight, but this isn’t a man who got here fast or expected to get here at all. The day AC Milan took over the Avila academy, where he had started work coaching eight-year-olds, changed his life. He got his first senior job at 21 but even then there were moments he was ready to walk, resigned to getting back behind the wheel.

Called to coach Valladolid’s B team, he went to Izarra, Rápido de Bouzas, Cartagena and Mirandés (where he worked with González), none of them above the third tier. And although he took two of them up, he didn’t go with them. Then a year ago, he went to Leganés and did it again, this time securing promotion from the second to the first division.

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Staying there wouldn’t be easy, they knew: only Sevilla and Espanyol, extreme cases with emergency measures imposed upon them by the league, have lower salary limits and few squads look as limited. Their summer signing, Sébastian Haller, a coup that excited everyone, has hardly played; the strikers who have, have hardly scored, De la Fuente, Munir, and García all with one. They arrived in Barcelona having lost four of seven and although they hadn’t finished a weekend in the relegation zone it was close now: they were two points off, having played two games more than Espanyol and Valencia, one more than Getafe. But, González said, there is personality there and there was something in Jiménez’s insistence last night that “we have to appreciate what this team is doing.”

What they had just done, no Leganés team had. They had beaten the league leaders, a little breathing room found and a moment too, one to hold on to whatever lies ahead. It was the first time Leganés had won at Barcelona, time to talk about Jimenez’s boys, footballers who had been through all sorts but not this. “I’m so happy to be able to live this moment; we have had a night we will never forget,” González said. “This is a lovely night, a historic one.”