Atletico Madrid travel to face Barca on Saturday, with an escalating civil war between its board and fans destabilising the club, and their team's form deserting them.
Top-flight debutants Xerez visit Real on Sunday for a classic David versus Goliath contest. The Andalucians have a budget of 9 million euros for this campaign - Real have 420 million euros to play with.
Fan protests at Atletico's lack of activity in the transfer market over the summer are threatening to turn into a full blown attempt to oust the majority shareholder Miguel Angel Gil, and the team's poor start is fanning the discontent.
Abel Resino's side fell 3-0 to Malaga on the opening day, drew 1-1 at home with 10-man Racing Santander last weekend, and only managed a 0-0 draw with APOEL Nicosia at home in the Champions League on Tuesday.
"It would be a lie to say this situation isn't affecting us," defender Luis Perea told a news conference. "The only way for us to put it right is by winning."
Atletico, who were trounced 6-1 in the same fixture last year, will be without first-choice goalkeeper Sergio Asenjo and defender Alvaro Dominguez who are on international duty with Spain at the Under-20 World Cup.
A MIRACLE
Where the pressure is on Atletico to perform at the Nou Camp, Xerez are under no illusions about their chances in the Spanish capital as they seek their first ever point in La Liga.
"With the names they have at Real Madrid this is going to be a very different game for us," said Xerez's Argentine defender Leandro. "It would be great to get a point ... a miracle."
Third-placed Valencia and last-season's King's Cup finalists Athletic Bilbao are the only other sides with 100 percent records. Valencia host Sporting Gijon on Sunday and Bilbao receive Villarreal on the same day at.
Valencia's flying start to the season owes much to the form of Spanish internationals David Villa and David Silva, whom they hung on to over the summer despite interest from a number of clubs.
"It's always difficult to compete with Real and Barca because of the money and the players they have, but we hope to be in the fight (for the title) and causing them problems," said Silva.
