Real Madrid said on Wednesday that Luka Modric and Marcelo have tested positive for coronavirus.
The experienced pair returned positive results in the latest round of routine squad tests and will now self-isolate.
Madrid, who beat Atletico Madrid 2-0 in the derby on Sunday, are next in action on Sunday, when they face Cadiz in La Liga.
While Marcelo, 33, has started just once for Madrid this season, Modric remains a key part of Carlo Ancelotti's side.
The midfielder, who turned 36 in September, excelled against Atleti as Los Blancos moved eight points clear of Sevilla at the top of the table.
Played 18 times
In total, he has played 18 times in all competitions this season.
Madrid face Athletic Bilbao on December 22 before resuming their season away to Getafe on January 2.
