Real Madrid have revealed that club captain Sergio Ramos picked up "a muscular injury" during Thursday's training session with the Spanish champions.
Madrid have not put a timeframe on the defender's return to action, but it is thought that the Spain international will miss the next two to three weeks of the campaign.
"Following tests carried out on Sergio Ramos by the Sanitas Real Madid Medical Services, he has been diagnosed with a muscular injury in the soleus of his left leg," read a club statement. "His recovery will continue to be assessed."
Los Blancos will return to La Liga action following the winter break with a trip to Celta Vigo on Sunday night.