Barcelona lost but no one said it; 24 hours later Real Madrid won, and brilliantly too, but still no one said it. Not this time. This time there was no Game On, no sign of the patented Crapping-yourself-ometer, no heebie-jeebies, no We're Coming For You, and not one headline declaring: Hay Liga. Translation: There is [a] league. Perhaps because everyone agreed that there isn't. There was a "We're Back!" but back where? "The league hasn't got closer in the slightest: there isn't enough garlic in the whole of Spain for Barcelona to feel Real Madrid's breath on the back of their necks," wrote David Gistau, speaking for pretty much everyone. Because here's the bottom line: the gap is still 15 points.

The gap? Hang on a minute, which gap? The gap between Real Madrid and Barcelona might be 15 points, but the gap at the top is eight points. While most naturally focus on the big two, a third team stands between them. It is Atlético Madrid who are second, seven points ahead of Real, and it is no fluke, no quirk of the fixture list: the season is 20 games old and everyone has played everyone else. Besides, it's not just this season, it's last season too. Time to take Atlético Madrid seriously. Maybe not to catch Barcelona – eight points remains huge and Barcelona's 3-2 defeat to Real Sociedad was their first in 20 games, only the second time they've dropped any points at all – but to compete for second.

After all, if it is hard to see Barcelona losing their grip on an eight-point lead, the same could be said of Atlético and their seven-point lead. And that's almost the most striking thing of all. There is a tranquillity, an optimism, a reliability, about Atlético unthinkable not so long ago.

When Diego Simeone took over in week 18 of last season, he was the 49th coach the club had employed under the current owners. Conflict was constant; stability impossible. Even success – and don't forget that they did win the 2010 Europa League – didn't bring peace. They were forever tottering on the edge of a cliff. Now, even problems don't knock them over the edge. On Sunday night Radamel Falcao picked up a muscle injury. No panic, no tears, no whine, just a smile. "He'll be a great addition to the squad when he comes back," Simeone said.

Falcao's loss will be huge, of course. The Tiger has been Atlético's outstanding performer this season, scorer of 18 goals (as many as Cristiano Ronaldo) and a man who boasts a startling effectiveness. His absence may well cost his team, even if it is only for three weeks. But it did not feel like an empty platitude this time. Simeone's words rarely do, even when that is exactly what they are, all commitment and effort and work.

Since Simeone arrived, something has changed at the Calderón. Some could see it coming from the start. Simeone had only been there a couple of weeks when one person close to the squad confided: "Something's changed." He added: "Cholo's different and so are the players: he's really sticking it to them and they're not rebelling. I've never seen them like this." Others had tried but failed. No other man could have united Atlético like Simeone has: a former club captain and double winner, an idol who always promised to return, his status is untouchable. At the training ground, in the boardroom and at the Calderón.

In the Atlético Madrid dressing room, only one person has a status even approaching his and that's Falcao whose very personality, seriousness and relationship with Simeone means that there is no challenge. Players who, in the words of one man at the club, "did whatever the hell they wanted," now daren't. Even the battle between the president, Enrique Cerezo, and the chief executive, Miguel-Angel Gil, the fault line that has undermined the club for years, has been somehow subsumed into Simeone, master of all he surveys. If players complain to the directors, their gripes go unheard. Suddenly, surprisingly, everyone is heading in the right direction.

"If we don't live for our work and effort we will be distracted by things that can do us lots of damage," Simeone said. "Simeone has changed our mentality," added Falcao. Yet he is close to his players too: one of the first things he told them was that fans had whistled him too. Together, they would win them over. Before the derby with Madrid, 21,000 fans turned up to watch them train and cheer the players on; when they inevitably lost the derby, it didn't matter for once. The fatalism was less, the impact mitigated. Incredibly, they were still ahead of their neighbours and the following week the Calderón was packed again … Atlético hammered Deportivo 6-0.

From the start there was another simple message: know your limitations. "As soon as we stop doing the right things we'll fail," the coach told his players. "We must be clear and we must be constant." On the opening day of the season, Atlético drew at Levante, despite having 69% of the ball. "We played the way the Spanish like, with lots of possession. But I want to have the ball less and make more chances," Simeone said. The comment contained a dig; it also contained an essential truth.

Exactly half a season later Atlético faced Levante again on Sunday night. Since that opening day, they have dropped points only four times – and two of those were away at Barcelona and Real Madrid, who both still have to come to the Calderón and who both know that it won't be easy. It is bigger even than that: Atlético finished last season in a European place, won the Europa League and hammered Chelsea in the European Super Cup. They have one foot in the Copa del Rey semi-final; a final against Madrid or Barcelona is a real possibility. So too is beating them.

Atlético have been one of the sides with the least possession this season, but they concede few chances and counter swiftly and effectively. No striker has been as effective as Falcao – in part, a product of the way he plays; in part, a product of the way that Atlético do. And after defeating Sevilla, their opponents' coach, Míchel, insisted: "Atlético can win the league. It is punch that sets the really big teams apart and they have it."

Eleven teams have completed more passes than them but only Osasuna and Real Sociedad have put more balls into the box and only Real Madrid and Barcelona have scored more goals. They're 11 goals ahead of anyone else. Bit by bit, they are starting to dominate teams too, taking control of the ball and pushing opponents back. Yet they remain hard to break down. Thibault Courtois is one of Spain's best goalkeepers and has consistently impressed – he made an astonishing string of saves against Betis in the Copa del Rey – yet he has had to make fewer stops than any other goalkeeper. And only Málaga have conceded fewer goals.

Atlético are aggressive and competitive, fast and physical; as the Spanish definition has it they are pesado, hard-going, insistent, heavy. Speaking of which, at the end of the game there was a confrontation in the tunnel between Simeone and the Levante captain, Sergio Ballesteros. Simeone did not run, nor complain; there was a kind of added strength in his silence, almost an admiration for his adversary. "Ballesteros defends his club and I defend ours," he said.

It is almost the perfect definition of Simeone and his team: never back down, never lose your cool, never desist. "They undo you with their intensity," said the Levante manager, Juan Ignacio Martínez. Right from the start. They have gone into the half-time break in the lead in 12 of their last 16 games at home; not once have they headed for the dressing room trailing.

On Sunday night, Atlético defeated Levante 2-0, Adrián scored the first and Koke curled in a lovely second. It was Atlético's 11th league game at home this season: they have won all 11. In total, counting Copa del Rey and Europa League, it was their 17th game at the Calderón. Seventeen games, 17 wins. Including last season's final match, they have won 12 in a row at home in the league, equalling a record they set between December 1939 and October 1940, when they were Atlético Aviación – the real régime team. They haven't even conceded a goal in their past 10 home matches.

"Can Atlético win the league", the Levante manager was asked. "Why not?" he replied. The answer is probably: "Barcelona." Once upon a time, it would have been: "because they're Atlético Madrid."

Talking points

• "They're mortal," ran the cover of Marca, while the cartoon on the back of Sport showed a doctor examining their skull and concluding "they are human after all … apart from Messi." Messi claimed another record by scoring for the 10th successive league game, but Barcelona were beaten for the first time this season, 3-2 at Real Sociedad. It had taken 20 weeks and Barcelona had lasted longer than anyone else in Europe. "It had to happen sometime," Messi said. But did it? Some had started to wonder if they might complete an unbeaten season.

Defeat could be explained: Barcelona were down to 10 men after the sending off of Gerard Piqué for two yellows (both daft, both a little light but both absolutely correct), they had twice hit the post at 2-0 and there had been missed chances. The defending on la Real's second and third was a tad ropey. Besides, la Real are a good side when they get it right. And, besides, Barcelona have form: they've not won at Anoeta since 2007 and blew a 2-0 lead last year too. They also came off the back of drawing 2-2 with Málaga in the Copa del Rey having led 2-0. No panic. But said Tito Vilanova: "This puts us in our place."

• Emotionally, something shifted this weekend. Madrid surely know that the league is lost but there was a different mind-set after Barcelona lost and they battered Valencia. The first half was the Madrid side from last season: counterattacking with barely believable speed and precision. The perfect storm, utterly unstoppable. Not that Valencia tried to: they played high but without any pressure, and got blown to bits, Madrid sprinting into the space behind them at will. Ronaldo scored twice and provided a brilliant assist, Angel Di María got two ("that shut some mouths up," he said), and Mesut Ozil was superb. The first came from that familiar source: the other team's corner. In a flash, the ball was in the net at the other end, scored by Gonzalo Higuaín.

• Javier Aguirre, miracle man. Espanyol won again. That's just one defeat in six under him since he took over from Mauricio Pochettino.

• Unai Emery is back, prowling touchlines, waving his hands around and speaking at 100 mph. He's the new Sevilla manager but he could not start with a win. Sevilla's lead was gone with the wind … quite literally. 1-0 up at Getafe, the equaliser came when Adrián Colunga's curling free-kick got picked up by wind and carried over Palop and into the net. Respect to Getafe's fans, by the way; there may not be many of them but those that there are there are pretty loyal. It was miserable out there and they stuck it out.

• Dear Rayo Vallecano fans: sorry about that.

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

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