Spain's biggest game of the season so far takes place this Saturday and, for once, it is not el clasico.
The Madrid derby between Atletico and Real is the most intriguing for years. Normally, the grander, more successful club from the wealthier northern side of Spain's capital beats the smaller but still huge club from the south side.
Indeed, Atletico have a dire recent record in derby matches and have not won at the Bernabeu for 13 years, betrayed by a habit of falling apart and behaving like they are awestruck.
Madrid show no mercy to their neighbours - and not only Atletico. They have won every single derby, 16 in total, against Atletico and fellow Madrid sides Getafe and Rayo Vallecano since 2008, until, tellingly, this season, when Getafe won 2-1.
Atletico normally go into the games well behind Madrid in the league. Not now. Diego Simeone's side are eight points clear of Jose Mourinho's charges after 13 Primera Liga games.
They have not finished above Madrid since 1996 when they won the league, that underdog status intensifying their fans' loathing towards the Whites.
Madrid have already lost five games this season, more in three months than in the whole of last term.
Not just Barcelona and Lionel Messi are pulling away in the Primera Liga and Pichichi chart, Atletico are doing it in the league. But can they widen the gap by beating Madrid?
Their top-scorer Radamel Falcao says they are not going for a draw - as you would expect.
He has played in the far more challenging environment of derby matches in Buenos Aires in Argentina and so has the other man responsible for the Atletico revolution, their Argentine coach Simeone.
Simeone has instilled a toughness in his side which has seen them win the Europa League and European Super Cup in style in 2012, as well as 11 of their opening 13 league games, with only a single defeat.
Atletico need to be tough - they face Madrid and Barcelona away in two of their next three fixtures.
The neutrals who despise the two team dominance in Spain are hoping they can hold out.