Lionel Messi Photo: VCG
They are the two biggest teams in Spain and arguably European - if not world - football.
But Barcelona and Real Madrid are not having it all their own ways this season.
In fact, it is a season that could be described as a crisis for both managers, Real Madrid's Zinedine Zidane and Ronald Koeman at Barcelona.
Both men are former players of their respective clubs, and European Cup/Champions League winners with them to boot. Yet club legend status - and in Zidane's case winning three Champions League trophies as a manager - does not make them immune from the axe.
It got closer for Koeman, the former Netherlands international player and manager who only arrived at the Camp Nou in the summer.
"I can't explain it," Koeman said of the goal scored by Alvaro Negredo that confined them to a fourth defeat of the nascent La Liga season.
The goal came from a throw-in taken by Barcelona's Jordi Alba, which was then sliced by goalkeeper Marc Ter Stegen before Frenkie de Jong slid in as Negredo, as if in The Matrix, stood stock still to roll the ball into an emty net.
"You can't let in a goal like that. We have done quite a few, and it hurts," Koeman said.
"It's incredible that we lost because of a goal like that, it's an error you do not expect this team to make. It shows we were not concentrating," Koeman continued. "The attitude was not good tonight. I'm very disappointed."
The disappointment extended to his players. "Individual errors are costing us," veteran midfielder Sergio Busquets said after the latest loss, and it was arguably three individual errors that led to the decisive Negredo finish.
It was a goal that summed up Barcelona's La Liga struggles in a game that did much the same.
Once again they turned toward Lionel Messi, as they have so often done in the past, but this year - after a summer where he declared he wanted to leave before the board decided to air all of Barcelona's dirty laundry in public - the Argentine seems a little more human, by his own superhuman standards.
Koeman described the defeat to Cadiz as a "gigantic step backwards in our chances of fighting for the league" and history would suggest he is right, despite the hopes of the club's institutional director, Guillermo Amor.
"Just as we have dropped points, others will too," he said, but will they drop enough for Barcelona to get back into the title race?
They are already 12 points behind Diego Simeone's Atletico Madrid who top the table and they are six behind El Clasico rivals Real Madrid.
That is the same Real side who are in a crisis of their own, who went into last weekend's game against Sevilla aware that it was a week that would likely decide Zidane's fate.
He seemed aware of the fact before Real travelled to Andalusia, something that might have been made more clear by the fact that his side were to face Julen Lopetegui's Sevilla. Lopetegui was the man Zidane replaced when he last returned to the club, the former Spain man having lasted just 138 days.
"Yeah, yeah, for sure," Zidane said in his pre-match press conference about the week ahead which started with Sevilla before a vital Champions League game against Borussia Mönchengladbach and then the Madrid derby against the league leaders.
"For sure, but it's like always: There have been bad moments, criticism, and today's the same. Maybe more than before, but no problem: I'm not thinking about that. I feel like the players are going to do it on the pitch. Tomorrow is an opportunity to show that we're a good team."
They did not necessarily do that, but they did get a win. The decisive goal was given as an own goal to Sevilla goalkeeper Bono but it was enough for Zidane to make it to midweek and Monchengladbach - a game that finished 1-0 with Real still in the Champions League.
Can he ever feel safe knowing that he is never more than two bad results away from another Bernabeu exit?
"I never felt I was, never," Zidane said ahead of the Sevilla game. "Not as a player, a coach, or person. We're all here for a reason; I'm here for a reason [to win], and will be until the last day."
Zidane certainly made all the right noises ahead of the Sevilla win.
"It's a difficult moment but what matters is coming together, following the same path and we'll sort this out, for sure," he said.
"I feel the support from the club and from everyone. I can't be happy when we lose, no one can, the players included. But we now where we are: we're fortunate to be at this club. We have to connect to do well."
Their previous game had been a shock loss to Shakhtar Donetsk that made this week's Champions League game make or break. Real Madrid is not a team that plays on Thursday nights in the Europa League.
Zidane - again before Sevilla - was adamant that he would not resign. "No, I haven't thought about that at all."
But the decision will likely be out of his hands when it comes - and it will come, it always does at Real Madrid, just as it does at Barcelona.
Defeat at the weekend - where Barcelona face lowly Levante - could spell curtains for both Zidane and Koeman.
The situations at both clubs means that no matter whatever else is going on - and there is a lot going on at the Camp Nou and Bernabeu this season - it is on the pitch where the managers are judged.
It is not just on results but the style of winning itself. Expectation is such that the context of the crises behind the scenes do not matter and even wins for both at the weekend might merely be stays of execution.
Will either boss still be there when the sides meet in the next Clasico in April?