When Atletico Madrid won La Liga a couple of years ago - and came within a few seconds of adding the Champions League - it was widely perceived as a glorious but unrepeatable one-off: the right people in the right place at the right time.
Now, though, Atletico are contenders again. They are through to the Champions League knockout phase after winning their group and are level on points at the top of La Liga with Barcelona going into Saturday's trip to the Nou Camp (although Barca have a game in hand).
The man behind Atletico's success is manager Diego Simeone, the fiery Argentine who for many years was best known in England for his role in David Beckham's red card in the 1998 World Cup finals but is now firmly established as one of the game's finest coaches.
In recent weeks, Simeone has repeatedly been linked with a summer move to Chelsea, and that is no surprise considering his success at the Vicente Calderon.
When he returned to Atletico, who he had played for in December 2011, they had won only two trophies in 15 years. Under Simeone they have claimed five: the Europa League and Uefa Super Cup in 2012; the Copa del Rey in 2013; La Liga and the Spanish Super Cup in 2014.
And those triumphs are even more impressive when you consider they have been achieved on a fraction of the budgets enjoyed by Atletico's chief competitors, Real Madrid and Barcelona.
So it is clear Simeone is a very good manager indeed. But what makes him so special, what would he bring to the Premier League, and would he even consider making the move?
'Rigorous discipline, insatiable work ethic'
A cursory glance at statistics tells you Atletico's greatest quality is their defensive strength.
Their title-winning campaign was based upon by far the best defensive record in Spain and this season they have been even more difficult to score against, conceding only eight goals in 21 league games. Indeed, their record of just three goals conceded from the opening 11 away fixtures has never been achieved before in La Liga.
In part, Atletico's defensive excellence is down to the magnificence of Diego Godin, the impeccably reliable Uruguayan centre-back.
More than individuals, though, Atletico's resilience at the back can be explained by the rigorous positional discipline and insatiable work ethic instilled by Simeone, whose approach to football is regularly summed up with one word: intensity.
Those who remember Simeone's playing career will be familiar with that quality. He was a relentlessly hard-working midfielder who enjoyed great success with Atletico, Inter Milan, Lazio and the Argentina national team, among others.
He has now succeeded in transmitting that kind of passion into his players, and on matchdays he provides a powerful, prowling presence on the touchline - especially during home games, where he can be regularly seen turning to the Vicente Calderon fans and beseeching them to raise the volume of their support.
At times, Simeone's emotion can spill over. In the latter stages of the 2014 Champions League final defeat by Real, he was sent to the stands after running onto the pitch to rage at opposing defender Raphael Varane, and later in the year he received an eight-game ban after confronting the officials during another game against Real.
But he does seem to have calmed down since then, perhaps learning the lesson that his team suffers when his temper boils over. Or maybe the next explosion is just around the corner.
'There is a fallacy in the perception of Simeone'
There is, however, much more to Simeone's strategy than passion and discipline. One of his most vocal admirers is Michael Robinson, the former Liverpool and Republic of Ireland forward who finished his playing career in Spain and is now the country's foremost television analyst.
Speaking to BBC Sport, Robinson argues there is a great fallacy in the common perception of the Atletico boss, noting: "When someone has a reputation for a particular thing, it can be hard to shake off.
"People know Simeone was a hard player and that Atletico are a hard team, so they think it's all huff and puff, diligence and defending. But the truth is he's not at all one-dimensional - he's very astute tactically and a real admirer of talent.
"The year they won the league, he would often change the tactics three or four times a game. For example, they'd start by going long to Diego Costa, forcing the opposition to defend deeper, and then they could start to play shorter because they had created space."
|How much?! - comparing the costs of Barcelona and Atletico Madrid|
|Claudio Bravo £12m||Jan Oblak £16m|
|Dani Alves £35m||Juanfran £4m|
|Gerard Pique £5m||Diego Godin £8m|
|Javier Mascherano £20m||Jose Gimenez £1m|
|Jordi Alba £14m||Filipe Luis £16m|
|Ivan Rakitic £18m||Koke £0m|
|Sergio Busquets £0m||Gabi £3m|
|Andres Iniesta £0m||Saul £0m|
|Lionel Messi £0m||Yannick Carrasco £20m|
|Luis Suarez £81m||Antoine Griezmann £30m|
|Neymar £86m||Luciano Vietto £20m|
|Total Cost £271m||Total Costs £118m|
It is certainly true that Atletico's defensive sturdiness and propensity for scoring scrappy goals from set-pieces encourages onlookers to disregard the silkier aspects of their play, including Simeone's willingness to incorporate creative, flair players if they are also prepared to work hard.
In the past, that role was filled by Arda Turan, the gifted Turk who was signed last summer by Barcelona; now, a lighter touch to counterbalance the trademark intensity is provided by highly skilled performers such as Antoine Griezmann, Yannick Carrasco and Luciano Vietto.
Indeed, there is a growing sense the current Atletico crop plays in a very different manner to the team that shocked the football world by overcoming Barcelona and Real for the La Liga title two years ago.
"Simeone gives a concession to artistry," states Robinson. "One of his great strengths is taking artistic players and giving them his work ethic without sacrificing their flamboyance.
"I've seen Atletico grow, and in some ways they are now considerably better than the team which won the league - he has incorporated players with more natural talent and they can be very eloquent with the ball.
"He certainly isn't just an old-school manager who only tells his players to roll up their sleeves and get stuck in."
An admired and respected leader
From the way Atletico players regularly celebrate their goals by racing to the sidelines and embracing their manager, it is clear Simeone is greatly admired and respected within his squad.
In Spain, he is widely known by his nickname, 'El Cholo', and the past couple of years have seen 'Cholismo' reach almost cult-like status among followers who admire his maxims asserting nothing in life can be achieved without hard work and dedication.
Simeone loves Atletico's role as underdogs, regularly using their place in Barca and Real's shadows as a motivational tool - in the run-up to the 2014 title triumph he famously declared: "We see ourselves reflected in society, in people who have to fight. People identify with us. We're a source of hope."
But in addition to delivering stirring words, Simeone's astute football mind also allows him to get the most out of players by improving the technical and tactical aspects of their game.
A great example is Griezmann, who was always a highly regarded youngster during his early days with Real Sociedad but has rapidly matured into a world-class talent since joining Atletico in 2014.
"The change in Griezmann is quite wondrous," enthuses Robinson. "Cholo has converted him into a most unbelievable all-round forward, who will one second be making a tackle on the edge of his own area and the next be shooting on the edge of the other.
"It didn't happen overnight, but within the space of three months of working with Simeone there was a spectacular transition."
Will he be heading to England?
So, is this passionate, tactically astute, inspirational and, above all, successful manager ready to take his considerable talents to England? Not so fast.
This is not the first time Simeone has been linked with a move away from Atletico, with his title-winning exploits in 2014 inevitably resulting in similar speculation. But he rejected all advances and last year signed a new contract to stay with his current club until 2020.
"Why would he leave?" asks Robinson, who believes Simeone has more work to do at the Vicente Calderon.
"I think he's got a challenge here - he has already done away with the duopoly of Real Madrid and Barcelona, and now I think he's got the ambition to make Atletico Madrid natural contenders, or even favourites, for every competition they play in."
Of course, it could be argued that after so many years of lagging behind Real Madrid and Barcelona in financial terms, Simeone would relish the opportunity to join a club such as Chelsea where signing world-class talent became a realistic option.
But Atletico are rapidly growing off the pitch, boosted by additional revenue following their recent part-acquisition by the massive Chinese property investment company Wanda Group. And they will take another big step forward next year by moving into a new 70,000-capacity stadium.
|Elsewhere across La Liga on BBC Sport|
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|Chelsea and Ghana's Christian Atsu loaned to Malaga|
Although Robinson would not entirely rule out the prospect of Simeone abandoning Atletico at such an exciting period in their history, he can only foresee that scenario unfolding in a certain set of circumstances.
"Knowing Cholo, I don't think he's worried about cheque books or personal recognition," smiles Robinson. "He could leave if he falls out with someone at Atletico, or if he's getting bored, or if he feels the players are getting tired of listening to him.
"But for his career aspirations, I don't think he could go anywhere better."
So, Roman Abramovich, be warned: Simeone might be the man you want, but that doesn't necessarily mean you'll get him.