By the end of the first month the others had given up, unable to take any more, but he stuck it out – lying exposed and alone in the dark, 25km outside Asunción. At the tiny Estadio Ypané, a makeshift bed of blankets and cardboard lay in a stairwell beneath the stand, at the mercy of tropical heat and tropical storms. The boy from San Joaquín was 15 when he arrived; almost two years later, he was still there. Homeless, sleeping rough. He says it was "hell", "frightening and horrible." 250km away, his parents, poor land workers, were none the wiser: he never told them. By night, he paced about, drank cane liquor – "I was almost an alcoholic" – and slept. Or tried. By day, he did shifts at a sawmill. When there was work going. Which wasn't often.

That wasn't all he did. Nelson Antonio Haedo Valdez also played football, training with the Estadio Ypané's other tenants, second division side Atlético Tembetary – quite literally his home team. He had a promise to keep: his mother cried when Laurent Blanc knocked Paraguay out of the 1998 World Cup, so he vowed to make amends by scoring at the World Cup himself. And although he says he was "never a very good player", he has certainly never lacked character. Or heart. This is the man who, gun in hand, chased off thieves stealing his car and ran into his blazing home to save his dog; the man who sends €10,000 (£8,285) a month to his home town, where a community depends on him, and buys presents for 1,500 kids every Christmas.

The fact that these days he can owes much to a man called Jurgen Born, who worked for Deutsche Bank in Latin America. Thanks to him, instead of continuing to live under the stands like a troll under a bridge, Valdez crossed to Europe. "I saw a madman who never stopped running," Born remembers of youth team games in Ypané. One day he bought Valdez a ticket to Germany and got on the phone to Werder Bremen. They had no idea who he was but the president's wife, a fellow Paraguayan, convinced them to give Valdez a chance. He scored four times in his first game.

Yet while Valdez went from Werder Bremen's youth team to the first team, winning the league in 2003-04, while he played for his country and went from Borussia Dortmund to Spain this summer, becoming the most expensive player in Hércules' history, at €3.8m, he has rarely proven a prolific goalscorer. Generous and tireless, with shoulders almost as broad as his head, running through from deep, dropping off the front, focused more on aiding others, goalscoring has rarely been his role. He got a goal every four games for Bremen, 16 in 113 for Dortmund and nine in 38 for Paraguay. And when he did fulfil the promise he made his mother, against Spain in South Africa, they only went and took the goal off him. And a semi-final place with it.

On Saturday night, Valdez took revenge. Nine weeks later, nine years after he last lived under Atlético Tembetary's stands, Valdez got his goal. His goal -suh. Two of them. And not just any goals, either. Massive ones. The goals that sunk Xavi and Piqué, Iniesta, Pedro and Villa. Implausible goals. Impossible ones.

Because however much Herculés coach, Esteban "Sardine" Vigo, a former Barcelona player, predicted that his side would beat FC Barcelona 2-0 this weekend, most people thought he was off his head. Barcelona are the league champions; Herculés are making their first appearance in the first division since 1997 – in fact, they've spent just two of the last 26 years in the top flight. Hell, they've spent half of the last decade in the regionalised, four group, eighty-team Second Division B. And Barcelona had not been beaten by a newly promoted side for a decade.

Barcelona had won 17 out of 18 at home last season, drawing the other. They had not lost a league game at home for 16 months – and that didn't really count, what with it being a who-cares-we've-already-won-the-title defeat against Osasuna. You have to go back to February 2009 for their last 'real' defeat at home – and that was a miracle. Since Pep Guardiola made his managerial debut in La Liga they have not once been beaten by two goals in the league. And Valdez, the goalscorer who doesn't score, was making his La Liga debut. 2-0? To Herculés? With Valdez getting them both? On Catalonia's official holiday, too? No chance.

Except that the 'diada' marks the bloodiest of Catalan defeats. Except that Herculés have a bit of a habit of this. The last time they were in the first division, back in 1996-97, they beat Barcelona twice. 3-2 at Camp Nou and 2-1 at the Rico Pérez – the game that effectively cost Bobby Robson's side the title, handing it to Fabio Capello's Madrid. Thirteen years later, history might just have repeated itself. Last night's saw the two-point advantage over José Mourinho's Madrid disappear; Barça now trail by a point. Exactly what Vigo said would happen, happened.

"See," said Vigo, "I'm not mad after all." Valdez scrambled in the first from a Royston Drenthe free kick and coolly curled in the second after a perfectly launched break to give Herculés a 2-0 win. A proper 2-0 win. Defensive, sure. But deserved. Striker David Trézéguet, signed from Juventus, described Herculés's performance as "a la Italiana" and Vigo admitted that he took inspiration from Mourinho's tactics during Internazionale's trip to the Camp Nou in last year's Champions League. Only Herculés were better than Inter – people seem to have forgotten that Barcelona won the second leg and, but for a refereeing mistake in the last minute, should have gone through.

This time there were no ifs, no buts, and few caveats: it was true that Spain's trip to Argentina didn't help, that Barcelona looked tired, that the pitch was awful, and that Guardiola started without Dani Alves, Carles Puyol, Sergio Busquets and Xavi, but there were no complaints. Even the Catalan media found no fault. "Herculés", said Sport, "were stronger than Barcelona"; El Mundo Deportivo described them simply as "superior". While Barcelona had almost 80% of the possession, Herculés had as many shots and better ones too. Barça were heavy-legged, lacking in imagination; Herculés were superbly organised with Valdez, goals aside, playing a colossal role as a support striker turned central midfielder. "They played brilliantly. All I can do is congratulate them," said Guardiola, while Valdez beamed: "The key was solidarity and sacrifice. This is a dream come true."

And for once it didn't sound like just another empty cliche.

* Gracias to Diego and the Dandy.

Talking points

• For neutrals, Herculés's win was almost perfect. But "almost" is the word. Not only was it impossible not to be pleased for Valdez, it raised hopes that maybe, just maybe, Madrid and Barcelona won't completely walk every game in the league this season. It also suggested that Herculés – who have made some interesting signings – can survive. And, on the face of it, that is a good thing: Alicante is a city that should have a first division team and 2,500 fans travelled to Barcelona on Saturday – far more than most teams take away – while the club have sold more than 15,000 season tickets. And their home kit, sponsor-free, is cool. Almost as cool as Royston Ricky Drenthe, in fact. Plus, Esteban Vigo is a very likeable manager – and one with the record of having won two successive promotions from the second division to the first. Last time, Xérez didn't stick with him. They went straight back down. It would be nice if he doesn't.

But then there's that "almost" and it's an "almost" that was brought crashing home at the full time whistle when the camera panned to the directors' box at the Camp Nou. There, smoking a big cigar and looking extraordinarily smug, was Enrique Ortiz. Ortiz is the club's owner – and the man at the heart of match-fixing allegations, after phone-tap recordings suggested that he bought off opponents at the end of last season to ensure a first division place. In the end, the judge decided that the tapes could not be handed over to the football authorities as evidence because they were part of another on-going corruption case (the conversations had been stumbled across entirely accidentally), because they represented an invasion of privacy and because match fixing is not actually a criminal offence – at least not until 22 December when a new sports law comes into force. Spain's football authorities then decided not to even call on the players involved to testify until the season was already underway. Herculés – club captains Tote and Abraham Paz are the players involved, along with Ortiz - may well be innocent but it's still a scandal that nothing has been done. Yet again. And the pleasure of seeing Herculés on Saturday, the satisfaction of believing that they might survive in the first division, is tempered by the feeling that perhaps they shouldn't be there in the first place.

• The score coming in from Barcelona got the biggest roar of an otherwise largely tedious night at the Santiago Bernabéu. Real Madrid looked impenetrable defensively but, the excellent Mesut Ozil apart, lacked fluidity and creativity in attack. Meanwhile, Cristiano Ronaldo's obsession with shooting from everywhere and anywhere is getting out of hand. He had ten shots on Saturday night. Having drawn their first match 0-0 and taken until the 48th minute to get the only goal on Saturday night, Madrid have now – in goalscoring terms – officially made their worst ever start to a season. Ricardo Carvalho got the goal on a break away from an Osasuna attack. Everything's fine though: Madrid's assembly was yesterday and Florentino Pérez has made three promises - to put a roof on the Bernabéu, to build a Real Madrid theme park, and too win the club's 10th European Cup. Promises this column could swear it has heard somewhere before.

• There might not have been much "good" football but sometimes madness is just as much fun – times like Athletic versus Atlético, an intense, passionate and occasionally violent game. San Mamés is a proper stadium. Unlike certain other stadiums you could mention. A superb first from Forlán and a late second by Tiago means that Atlético stay top of the table. And on Sunday they play their easiest match of the season: against Barcelona at the Calderón. The signing of Diego Godín is exactly what Atlético needed. Keep an eye out for Athletic's left back Jon Aurtenetxe, by the way: he looks like he's going to be very, very good.

• Two matches, two 4-1 defeats. And even Arizmendi scored against them. Levante look doomed already.

• Pennant watch. Eh? Oh. Mind you, it's not as if his former side are up to much without him. Málaga's owner, Sheik Al-Thani, offered his players €6,000 each to beat Zaragoza. They had scored five in 34 minutes. When Leo Franco finally saved a shot at the sixth time of asking, Zaragoza's fans gave him a standing ovation. But things did actually get better. You wondered if the sheik then made the same offer to his opponents, just to liven things up a bit. Alas, Zaragoza could only get three.

• Results: Barcelona 0–2 Herculés, Valencia 1–0 Racing, Real Madrid 1–0 Osasuna, Athletic 1–2 Atlético, Zaragoza 3–5 Málaga, Getafe 4-1 Levante, Villarreal 4–0 Espanyol, Sevilla 0–0 Deportivo, Almería – Real Sociedad, tonight.