1. Iker Casillas v Victor Valdes
Spain captain Iker Casillas' position as first-choice goalkeeper for Vicente del Bosque at the World Cup finals is not in doubt, but he has not looked so assured recently, making some uncharacteristic errors.
Barcelona's Victor Valdes won the 'Zamora' award for the best record in La Liga last year and tops the charts again going into the 'Clasico'.
Like Casillas, Valdes is an excellent shot-stopper and his distribution from the back is the starting point for Barca's suffocating possession game.
Calls for the uncapped Valdes to go to South Africa as third-choice behind Casillas and Pepe Reina will increase if he outshines his opposite number on Saturday.
2. Xabi Alonso v Xavi
Spain midfielder Xavi makes Barcelona tick even if he doesn't necessarily dominate the headlines.
His slick link-up play is the very essence of Barca's style, and cutting the distribution lines from the diminutive playmaker is vital to breaking Barca's domination of the ball.
Xabi Alonso plays a similar role at Real, though has had less time to settle into the role.
He's a stronger physical presence and conducts affairs from a deeper lying position, but is often the starting point for Real's swift counter-attacks.
3. Gonzalo Higuain v Lionel Messi
If club form was anything to go by Argentina would be unstoppable at the World Cup finals with the goals of Higuain and Messi.
They top the La Liga goalscoring charts with 24 and 26 respectively, but while Messi's goal-scoring feats are hailed around the world, Higuain's contribution at Real is under the microscope.
The 22-year-old's gutsy displays have helped Real perform many of their trademark comebacks, flourishing in broken play with his surging runs into the area.
But he has gone missing in big games, where he has been let down by poor tactical awareness and a profligacy in front of goal.
He has, however, the perfect stage to prove his doubters wrong by stealing the limelight from perennial headline-maker Messi.
4. Cristiano Ronaldo v Zlatan Ibrahimovic
Ronaldo cost Real just over 90 million euros last summer, and Ibrahimovic moved to Barcelona in a deal worth around 60 million euros.
It's hard to judge the commercial impact of the respective signings on their clubs, but on the field of play the towering Swedish striker has gone closer to repaying some of the investment than his flashy Portuguese rival so far.
Ibrahimovic scored the game's only goal when Real visited Barcelona in November while Ronaldo missed his best chance when denied in a one-on-one with Valdes.
The former Inter Milan striker scored valuable away goals against Stuttgart and Arsenal in the Champions League to help Barca into the semi-finals.
Real slu
