Dani Alves, Carles Puyol, Gerard Pique, and Eric Abidal. That was the back four that won the most famous Clasico of the last decade, a 5-0 thrashing Barcelona levied on Real Madrid at the Camp Nou in 2010.
All four were out the last time the two teams faced each other, with Alves playing less than a half before going down injured and the rest completely unavailable. Despite playing at home and being in better form than Madrid, Barca were happy enough they ended up with a 2-2 draw.
The tables have turned.
Los Blancos will be without starting keeper Iker Casillas or three of their top defenders, Sergio Ramos, Pepe, and Fabio Coentrao, in the first leg of the Copa Del Rey Semifinal at the Santiago Bernabeu Stadium. Aside from the defensive absences, forward Angel Di Maria, one of the top assist-givers in Europe, will be out as well.
On the other hand, Barca will have surprisingly few absences. Defender Eric Abidal and manager Tito Vilanova continue their recovery from illness. Isaac Cuenca and Marc Muniesa are nearing recovery from long-term injuries, but they have yet to feature all season. Jonathan Dos Santos picked up an injury, but he's strictly a backup.
While Abidal was a starter until he was sidelined due to a liver tumor, the team has learned to adapt in his absence, with the emergence of Adriano Correia and the signing of Jordi Alba.
Isaac Cuenca started elimination Champions League games for Barca, but again the team has been without him for a while and learned to adapt. And certainly, there's no understating the influence of Vilanova.
Those absences will be felt, but suddenly losing key defenders at the same time is a huge burden as Barca came to know. And while it will take a while before Cuenca and Abidal are back to firing on all cylinders, the Madrid players serving a ban will be ready for the second leg.
For that reason, Barcelona must take their chance and try to impose a good lead in the first leg. But it won't be easy.
"You never know if it's the best moment," Sergio Busquets insisted at the press conference. It would be foolish to feel too much confidence going into the Bernabeu.
Real will have the crowd behind them, for one. Second, they will have some good replacement options. Most teams would be quite happy to field Raphael Varane, Jose Callejon, or Alvaro Arbeloa as regular starters. New signing Diego Lopez or Antonio Adan will be Casillas's replacement. Coach Jose Mourinho even said Adan was a better option to Casillas at times. (Make of that what you will.)
Finally, Madrid still have lots of star power. Karim Benzema can assist or score on a moment's notice. Mesut Ozil may be the best passer in the world not playing for Barcelona. Sami Khedira can attack or defend with quality, while Xabi Alonso may be the world's best at long range passing.
And of course there is Cristiano Ronaldo.
Yes, Real Madrid are incredibly talented and it won't be easy. But this match-up will never be easy. Yes, coming in expecting it to win handily would be a mistake. But not striking a weak spot would be worse.
Even given the obvious difficulty in such a tie, Barcelona should be ready to attack.