On Saturday, football fans are awaiting the start of a breathtaking marathon - Madrid and will enter the first of four battles over the next 18 days.
Experts have no doubt - the outcomes of these matches will determine the teams' seasons.
The first clash will take place in the Spanish championship, the second on Wednesday - the King's Cup final, and on April 27 and May 4, the semifinals of the Champions League will take place.
In the national championships, there seems to be little intrigue at first glance - "Barcelona" has a solid eight-point advantage, so they can afford the luxury of not complicating the situation too much even if they lose.
"We have a great opportunity to deliver a decisive blow," confirmed Pep Guardiola, the coach of "Barcelona."
It is undeniable that the matches will have a significant psychological impact, as the team that performs better will gain confidence in their abilities for the upcoming duels.
However, "Real" coach Mourinho denied this: "What happens in one match has no influence on another. Many people think that the winner of the first match will gain an advantage. But my view is simple - you play one game, and when it's over, you think about the next one."
This was echoed by the most productive player of the capital team, Cristiano Ronaldo: "He who laughs last, laughs longest. I hope this will be us."
The statistics favor the Catalans - Guardiola has won all five "El Clasico" duels since becoming head coach in 2008. The most recent one was the most remarkable - "Real" was beaten 5-0 in Barcelona.
However, "Real" should not be dismayed - after injuries, midfielder Kaka and forwards Karim Benzema and Gonzalo Higuain are returning to the lineup.
Meanwhile, "Barcelona", whose selection of players is already limited, has lost defender Carles Puyol and Eric Abidal. Therefore, Guardiola is left with only two nominal center-backs - Gerard Pique and Gabriel Milito. Sometimes in this position, Sergio Busquets and Javier Mascherano were used, but Mascherano will be suspended on Saturday.
Forward Bojan Krkic will not play either, so Guardiola hopes that David Villa will end his nine-game scoreless streak. Otherwise, they may have to rely on the unstoppable Lionel Messi again - the best player on the planet has already scored 48 goals this season and set a new club record.