Barcelona defender Samuel Aumetti suffers from a muscle breakdown that will prevent him from playing for a month.
The injury was exposed to him
The second half of their 2-2 draw at home against Celta Vigo in the 14th round of the Spanish league.
Ommetti suddenly stopped in a pursuit with Celta Vigo's Yago Aspas to kick the ball and pass the ball from Maximiliano Gomez's precious equalizer.
The end-of-match tests showed that he had a right-leg muscle rupture requiring eight weeks of treatment.
Omtiti will be officially absent from the Clasico match, which will reunite Barcelona and Real Madrid on 23 December.