Barcelona will face their first Clasico since 2007 without Lionel Messi after the Catalans' captain sustained a fractured arm against Sevilla.
Messi had already set one goal up and scored another in Saturday's top-of-the-table clash at Camp Nou before he fell awkwardly.
The five-time Ballon d'Or winner was in obvious pain, although Barca's medical team dressed his right arm and it initially appeared as though he may attempt to play on.
Messi was withdrawn after a long delay, however, and Barca confirmed in a statement after their 4-2 win that tests showed a fracture in his right arm.
It means next Sunday's match between Barca and Real Madrid will be the first Clasico without either Messi or Ronaldo for 11 years.
Using Opta numbers, we assess Messi's record in one of the world's most important football fixtures.
38 - Messi has played in 38 Clasico matches for Barca, with the Catalan side winning 17 of those meetings and losing 12
26 - The Barca captain has scored 26 goals against Real Madrid, finding the net in four of his last five appearances in the Clasico
2 - Messi has twice scored a Clasico hat-trick, the first coming in March 2007 and the second coming seven years later at the Santiago Bernabeu
8 - Of Messi's 38 appearances in the Clasico, eight have come in finals, including the Supercopa de Espana. In those games, he has scored six times.
35 - Messi has featured in 35 consecutive Clasico matches for Barca, last missing a meeting with Madrid in 2007 when he had a thigh injury
2 - Barca have played two Clasicos without Messi since his debut, with Frank Rijkaard's men drawing 1-1 at home in 2006 and losing 1-0 away the following year