Real Madrid could be without the services of Karim Benzema for the trip to Barcelona later this month, with the club confirming that the centre-forward has a hamstring problem.
Benzema was replaced at the interval of Madrid's 1-0 defeat to Alaves at the weekend.
There has been no timescale placed on the striker's recovery, although it is thought that the Frenchman could spend at least the next two weeks on the sidelines.
Los Blancos travel to Barcelona for the first El Clasico of the season on October 28, and Benzema has emerged as a doubt for the struggling European Cup holders.
"Following tests carried out today on our player Karim Benzema by the Real Madrid Sanitas medical team, he has been diagnosed with an injury to his right hamstring. His recovery will continue to be assessed," read a statement on Real Madrid's official website.
Julen Lopetegui's side have lost three of their last four matches in all competitions, failing to score in the process.