Story highlights Real host Barcelona on 23 December Barca are 11 points ahead of Real in La Liga Barca have won five of last 10 matches (CNN)It is a rivalry like no other, a match which permeates beyond the white lines of the football pitch. It’s a complex cocktail of sport and politics. It’s the biggest game on earth. On Saturday, millions will watch arch enemies Real Madrid and Barcelona — two of the most successful clubs in history, boasting two of the world’s greatest players — battle it out in the 236th edition of the game dubbed El Clasico. Trailing their great rivals by 11 points in the league, Real — who last week won the Club World Cup — cannot afford to slip up at home if they are to retain hopes of winning the Spanish league title. Adding spice to the mix is the form of Lionel Messi, the all-time leading scorer in El Clasico history, who has notched 14 goals in 16 La Liga matches this season, overshadowing his long-time foe Cristiano Ronaldo, scorer of four league goals in 11 and recent recipient of a fifth Ballon d’Or. Follow @cnnsport But, as everybody knows, El Clasico…