Hugo Mallo boarded the bus on Friday afternoon, joining his mates from the Celta Vigo Supporters Club, the Peña Iago Aspas. "I wanted to experience it in a special way," he said. They'd been waiting for this moment for six years: at last, a Galician derby in the First Division, a top flight trip to Estadio Riazor for Deportivo La Coruña versus Celta. There were 160 kilometres to cover, north through the rías, time for a song or two, jokes and stories. Someone gleefully passed a mock 'For Sale' sign down the bus: Deportivo La Coruña, their rivals, racked by financial crisis and packed with Jorge Mendes's clients, their soul sold. More laughs, a photo: Hugo with the sign.

The bus arrived early in La Coruña, parking up with the sign in its window, Deportivo badge superimposed with a Portuguese flag. In they went, almost two hours before kick-off, and took up their position high in the stands, a metal fence and a handful of police in riot gear separating them from the home supporters. Hugo crossed himself, looked to the heavens; nerves, anticipation. In the summer, both Galician teams came up, now both could go down: bottom versus second bottom. Depor were nine points off safety. "We can push them down, leaving them with two feet in the Second Division," declared Iago Aspas, the 25-year-old Celta player in whose honour the Supporters' Club was named.

It was dark but Hugo wore sunglasses and pulled his hood over his head. And then, at 9.45pm, it began. Up in the stands, he shouted and jeered and swore. Standing by the fence, he gestured to the supporters on the other side to come and have a go if they thought they were hard enough. "You and you," he mouthed, pointing, gesturing to them that they had their gonads somewhere in their throat, the cowards. Their gonads and more: thrusting his hips up against the metal barrier, grabbing at his crotch, he called for them to come and kiss it. Then he enquired about their mothers. Eventually, a policeman in riot gear intervened and told him to sit down.

The tension grew. Down on the pitch, it wasn't going well. Celta were a goal down after just nine minutes and eventually lost 3-1.

Juan Carlos Valerón, 37 now but as classy in slow-motion as ever, clipped in a beautiful, delicate assist for Riki to control and volley the opener. Sílvio smashed in a rocket for the second just after the hour to send Fernando Vázquez, Depor's third coach of the season, off on one of those Fernando Vázquez runs, hopping and skipping and leaping along the touchline, clenching his fists. And then Diogo Salomão, on the pitch less than a minute, made it 3-0. Park Chu-Young's goal two minutes later was no consolation. Depor had raced through the game, intense and irresistible and the chances kept coming, the team roared forward with every touch.

The noise was deafening, blue and white flags packed Riazor, and Valerón and Riki departed to standing ovations. This was Depor's big night. A Mexican wave flashed round the stands, and a song: "Coruña entera, se va de borrachera!" The whole of Coruña is going out on the piss! Most of all though they chanted: "Sí, se puede!" "Yes, we can!". And for the first time in a long time there was a bit of hope: maybe they could. "We were running out of petrol," Vázquez said. "Now we have put a little bit back in the tank. Only a little, but it is there." Next up, two more direct clashes: Mallorca and Zaragoza. Rather than sink their rivals, Celta had given them hope; meanwhile, they had been dragged further into the fight, three from safety.

Hugo left the stadium in silence, head down, defeated. "I couldn't sleep," he admitted the following morning.

None of which would be particularly unusual, but for one thing: Hugo Mallo is not just a Celta Vigo fan, he is a Celta Vigo player and those cameras pointing his way were TV cameras. As for the camera phone pictures of him with the sign, they'd already found their way onto Twitter by the time he'd made it into the stadium. Ruled out because of a knee injury, Mallo, a 21-year-old full-back who was born in Marín and has been at Celta since he was a kid, had travelled with the supporters' club to see the game.

When the coach, Abel Resino, was asked about the picture after the game, he pulled a face. "I haven't seen it and don't know what you're talking about," he said. He was one of the very few. The club had been alerted to it before the game and tried to call Mallo only to find that his phone was off. "It ran out of battery," he explained the following morning.

Before the TV footage had been released in full, Mallo asked to appear before the press, where he apologised. "It was supposed to be a picture amongst friends," he said. "I am sorry if it offended anyone which it seems it did. I have to realise that I am a professional and I can't do that." The problem was that whilst his exploits could be explained as a joke amongst friends that unintentionally slipped out, with no malicious intent, the TV footage took it on a step. Celta have announced that they will hand down an "exemplary" punishment.

Besides, that was just the half of it. It was not just Mallo; it was also the man whose supporters' club he travelled with, his best friend in the squad. Celta's great hope.

In the peña, they could hardly love Iago Aspas more. He is Celta's best, most technically gifted player, . He is also one of them. Born in Moaña, he joined Celta at the age of eight, scored the goal that rescued them from relegation to the four-group, regionalised, semi-professional Second Division B, a pit from which they may never have emerged; last year he scored the 23 goals that helped them return to the First Division; and this season he is top scorer again. Better still, he is a self-declared "celtista until I die" and anti-deportista who says he'd never sign for Depor nor get a girlfriend from Coruña, who always wanted to be Alexandr Mostovoi and described Vagner Love booting Diego Tristán in the air as one of his favourite derby moments.

"Some people don't tell the truth in football," he shrugged. "I do."

Recently, he has told the truth, his truth, a little less, warned of the repercussion of his words. In his final season at juvenil level he missed nine of 30 matches through suspensions and he admitted: "I am tense on the pitch and make mistakes" but he had been trying, and mostly succeeding, to tame his temper. He has picked up just four yellows in the league this season.

But this time he could not help himself. When it comes to Celta, Aspas cares. Perhaps too much. In four games against Depor he is yet to score and this time far worse. First called up to train with the first team squad by Fernando Vázquez – in the other dugout on Friday night – in an interview not so long ago, Aspas recalled how he missed out on being included in the squad for the first time after being sent off for the youth team for a stray elbow. As if that was not bad enough, the game he missed was against Deportivo at Riazor. "I cried for days over an act of stupidity that lasted five seconds," he said.

These tears could last longer. Aspas wanted to leave Depor with two feet in the second division; instead, he has left them a foothold in the first – a shaky one, but a foothold nonetheless – and left his own side tumbling head-first towards relegation.

The game was not even half an hour old but Celta were already trailing 1-0 when Aspas clashed with the wiliest of wily old foxes, Carlos Marchena. As the two got up on the edge of the Depor area, Aspas leaned forward and seemed to headbutt Marchena. The red card was his first in almost a year and it was costly; any chance of winning virtually evaporated.

"When you're down to 10 men, things get harder," said Resino. "And when the man missing is Aspas, your problems multiply." Worse, Aspas is the only player in the Celta squad to have played every game, he has scored more than twice as many as anyone else goals than anyone else on 10, and he is the top assist provider, on seven. He is likely to get at least a four-match ban. Celta have won just one in 10 matches anyway; it is tempting to conclude that their chances of winning further games disappeared with Iago as he headed down the tunnel. His big night, their hope, destroyed.

"We were optimistic, but the opposite happened: we could have pulled out of the relegation zone but things turned out the other way round," said veteran Celta striker Mario Bermejo. "Iago has to realise that this is not a school playground. And sadly, yes, I did see the Hugo Mallo picture. We are a total disaster and we have to deal with [their] stupidity. We lack maturity: we have to realise that we represent a city and a club.

"When you go to bed with children, you wake up covered in piss."

Talking points

• Real Sociedad: if you can, watch their goals. Superb. They're now fourth, two ahead of Valencia and three ahead of Málaga.

• Luka Modrić: whoosh! Mesut Özil: woof! It was the Spurs in Spain game at the Santiago Bernabéu and for the first half, Alan Hutton's (and Gio dos Santos's) Mallorca were the better side against Modrić's Madrid. But then José Mourinho threw on Özil and Benzema and Madrid blitzed them, scoring three in five minutes, led by the German. "Sometimes it is like a revolution," said Sergio Ramos of the half-time changes. "At one point we made some of the home fans whistle Madrid – and that tells you how well we played," Gregorio Manzano added. Mallorca had won the two previous games. They remain in the relegation zone but there is optimism now: survival looks possible.

• Not least because Zaragoza are so dire. "We need bollocks," Manolo Jiménez insisted last week, reverting to type. The problem is not so much that they need bollocks as that they are bollocks. They have still not won in 2013, and they face Madrid next.

• Two more goals for Messi but that's not the story. He has got 42 league goals, already enough, with 10 games remaining, to have won every single top scorer award in every season in history except last season – when he got 50. But again, that's not the story. He has also scored in the last 18 consecutive league games. Oh, and one of them was a real beauty. But that's not the story either. Which in itself says something about the ordinariness of his extraordinariness. The story is the role played by David Villa, who scored the other and provided both of Messi's goals. Also worth noting is that Barcelona had their lowest possession all season at 54% and for the first time an opposition player made the game's most passes – step forward Rayo Vallecano's Roberto Trashorras – whilst Raúl Tamudo came on, got whistled and less than a minute later, scored.

• This weekend the league decided to try out a new way to foment respect for referees. Espanyol and Málaga were invited to share a drink and a chat with each other and the referee after their game. Cue awkward chats and a speedy getaway from the handful of players who went at all. Today, coaches are invited to meet referees and have doubts explained. Betis manager Pepe Mel is looking forward to it: "maybe they can explain to me how a foul outside the area ends up inside the area."

Results: Deportivo 3-1 Celta, Real Sociedad 4-1 Valladolid, Getafe 1-0 Athletic, Real Madrid 5-2 Mallorca, Valencia 3-0 Real Betis, Málaga 2-0 Espanyol, Sevilla 4-0 Zaragoza, Osasuna 0-2 Atlético Madrid, Barcelona 3-1 Rayo Vallecano, Granada 1-1 Levante.