Madrid: Real Madrid's Sergio Ramos and Barcelona's Gerard Pique share a rivalry every bit as intense as that between their teams.
Ramos is Madrid's perennial hero, the man who scores last-minute goals to win cup finals and keep the team alive when all hope seems lost.
As such, he feeds into Los Blancos' history of against-the-odds comebacks. Even on Tuesday, when Ramos scored an own goal to take the Champions League clash with Bayern Munich to extra time, he made amends by crossing for Cristiano Ronaldo to score the goal that effectively sent Madrid through to the semifinals.
Pique, on the other hand, is a Catalan icon and symbol of the resistance against Madrid, both in footballing and political terms.
Barcelona fans adore the way he speaks out against perceived injustices against his side, using social media for widespread impact. Although not one of the club's four captains, he is viewed as their leader and a future president.
An enduring image of Pique is the defender gleefully holding his hand aloft, five fingers outstretched, to represent each of the goals Barcelona netted in their 5-0 win over Madrid at Camp Nou in November, 2010.
The pair has had many run-ins and the build-up to Sunday's Clasico was no different, Pique making reference on Twitter to poor officiating in Madrid's 4-2 win over Bayern.
Ramos hit back, telling Pique he can "rewind and say the same thing about the PSG game" that saw Barcelona qualify for the quarterfinals in controversial circumstances.
Despite the bickering, the two share an underlying respect and call a truce when they play together for Spain.
"Pique and I like to throw each other pebbles, but as soon as I see him, I'm going to give him a hug," explained Ramos.
"It's the rivalry between Real Madrid and Barcelona, that will always exist. I'm not going to deny that we have become accustomed to it. We don't take it badly, it's all very sporting."
For defenders they are remarkably prolific and it would not be strange if, despite all the attacking talent on show at the Santiago Bernabeu on Sunday, one of them ended up settling the game.
If that happens — and probably even if it doesn't — expect there to be fallout, on the pitch, in spiky post-match comments and on social media.