When the teams meet at the Estadio Vicente Calderon this evening, it will be the final round of matches in the first half of the La Liga season, and an opportunity for either side to take a clear lead at the top of the table. Barcelona were once considered beyond the reach of opponents, but Atletico have dismantled convention.
They began with their own fortunes. This was a club renowned for its state of unrest and its unerring ability to collapse into a crisis. Managers were discarded, finances were fraught and the only certainties were that Real Madrid would win the derbies and that Atletico were more likely to dwell on failure rather than glory.
Then Diego Simeone arrived as manager in December 2011, and the club won the Europa League in 2012, the Super Cup in 2012 and the Copa del Ray last year. That last trophy was won at Estadio Santiago Bernabeu - a cathartic moment for a team always overshadowed by their rivals - and a second consecutive victory was achieved at the same ground this season.
That was Atletico's first league win at the Bernabeu this century. Since 2009 Atletico have won more trophies than Real and Simeone won more trophies in 18 months than Jose Mourinho did in three years. Only Barcelona have remained unmoved by Atletico's rise to prominence, since Simeone is yet to earn a victory over the Catalan side in three attempts. Yet the manager, who captained Atletico to the league and cup double in 1996, has revitalised his side.
Although the team ought to be the third best side in Spain, in budget terms, out-performing Real and being on a par with Barcelona is over-achieving. That is almost entirely down to the manager, who instilled his own values and personality on the squad.
Others have tried to impose discipline and a strong work ethic, but there was always an element of discord. The boardroom, too, could house resentments, but Simeone was able to apply his authority because of his status at the club.
Simeone demands industry and application from his team, but also a shared sense of responsibility. He underplays the extent of his own influence, which only strengthens the bond with his players. He is an unrelenting presence and that is reflected in a side that is extremely well drilled. No team has conceded fewer than the 11 goals that Atletico have lost this season, while only Barcelona and Real Madrid have scored more than Atletico's 47.
Atletico's expertise has been in stifling opponents and striking them down on the counter attack. They have become more progressive this season, though, without diminishing their solidity. Simeone tends to play a 4-4-2, with his two wide players tucking infield to provide creativity from varied areas but also to stiffen the midfield.
Up front, David Villa has developed an effective partnership with Diego Costa, the Brazilian-born attacker who has chosen to play for Spain at the World Cup. The latter is the embodiment of Simeone's work, since previous managers could not curb the erratic and often fractious nature of Costa's game, yet he is now one of La Liga's most effective and consistent forwards.
Atletico still look to counter swiftly, and dynamism and aggression is ingrained into the side. So, too, is selflessness.
When Simeone won the manager of the year award for 2013, he insisted that the ceremony did not take place ahead of a La Liga game against Valencia, because he wanted the focus to be on the match.
Atletico won 3-0. They also qualified for the Champions League knockout phase with 16 points and, drawn against AC Milan, are an outside bet to win the trophy.
There are anxieties, since around £40m will need to be found to pay a tax bill, while fit-again Lionel Messi has scored more goals against Atletico than any other side. None the less, there is nothing for Simeone's team to fear.
They have earned the right to be considered title contenders.