Real Madrid captain Sergio Ramos has been left disgruntled as La Liga scheduling means Barcelona have a longer rest period before the rearranged Clásico.
The match was originally set for October 26 at Camp Nou, but was postponed after political unrest in Catalonia led to security concerns
The two sides have now agreed with La Liga that the first El Clásico of the season will take place on December 18 at 20.00 local time (19.00 GMT).
However, Ramos has been left aggrieved by this decision, as Barcelona travel to Real Sociedad at 16.00 CET on Saturday December 14, while Real Madrid do not play until 21.00 on the Sunday when they face a trip to Valencia. This leaves the Catalan side with an additional 29 hours of rest over Los Blancos.
As quoted by the Evening Standard, Ramos said: "In the end, the only one affected is Real Madrid. But we are affected because we should be playing the same day as Barca and we should have the same amount of rest."
With the top of La Liga's table extremely tight this season, the greater rest period that Barcelona will enjoy before El Clásico could prove pivotal in not just the match, but the title race itself.
Just goal difference separates Barcelona and Real Madrid at the La Liga summit, with the former leading by a mere two goals. Breathing down their necks are Atletico Madrid and Sevilla, who are just one point behind.
Real Sociedad, who Barcelona play four days before the Clásico, are a further point behind. With such fine margins crucial in the most open title race La Liga has seen in a long time, it is little wonder Ramos and Real Madrid have been left frustrated by the fixture scheduling.
Although unhappy with the decision, Ramos is adamant that Barcelona's increased rest period will not impact Real Madrid's attitude before the fixture.
The Real Madrid defender added: "But in any case, we will go there with enthusiasm and ready to win the game."