Atletico Madrid have confirmed that Diego Godin and Augusto Fernandez suffered knee ligament injuries in Saturday's defeat to Barcelona.
Fernandez was substituted with 15 minutes remaining in the 2-1 loss, with Atletico already down to nine men after Godin followed Filipe Luis in being sent off.
The Uruguay defender had also suffered an injury early in the game, though, as his club revealed in a statement on their official website.
It read: "Diego Godin has undergone radiological tests on Sunday at the FREMAP Majadahonda Hospital, which confirmed the injury to his left knee.
"The Uruguayan international suffered 'a sprain (Grade I) on the internal lateral ligament in his left knee'."
Fernandez visited the same hospital on Sunday and received similar news.
Another club statement read: "After the tests, the medical report indicates that the Atletico midfielder suffered 'a partial tear of the medial collateral ligament in his left knee'."
No timescale was placed on either player's recovery.