Another crucial duel will be between Vinícius and Mbappé and FC Barcelona's offside trap. Last season, Barcelona's trap caught Real Madrid offside 12 times, with Mbappé being flagged eight times and Vinícius three. Real Madrid has made improvements in this area, but their new system under Xabi Alonso will be put to the test.

The battle between Mbappé and Wojciech Szczęsny will also be a key one. Mbappé has been in superb form, scoring 10 goals in nine appearances, and has a history of causing problems for Szczęsny, who will be looking to deny him.

Arda Güler and Pedri will also face off in midfield, both looking to drive their teams forward and control the tempo of the game. Both players have been thriving this season, with Güler and Mbappé leading the league in key passes.

Ronald Araújo may not start, but he could still play a key role off the bench, especially with Robert Lewandowski out injured. Araújo has shown his ability to score crucial goals, and Flick may consider using him as a makeshift centre-forward towards the end of the game.

These key matchups will likely decide the outcome of the El Clásico, and both teams will be looking to come out on top.