Four more Real Madrid players, including Gareth Bale, have tested positive for Covid-19 as clubs continue to struggle to contain outbreaks.
Marcelo and Luka Modric recorded positive tests earlier this week and will now be joined in isolation by Bale, Marco Asensio, Rodrygo and Andriy Lunin.
Carlo Ancelottti's son Davide, a coach at the club, has also tested positive.
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A statement from the club read: "Real Madrid CF reports that our players Asensio, Bale, Lunin and Rodrygo, and our first technical assistant Davide Ancelotti have tested positive for COVID-19."
Real Madrid continued their excellent start to the season with derby victory over Atletico on Sunday, and are eight points clear of second-placed Sevilla at the top of La Liga.
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However their next fixture against Cadiz, scheduled for Sunday 19 December, now appears to be in doubt.
The disruption comes in an untimely manner for the Spanish capital club - Ancelotti's side have won each of their last ten games, though the Italian claimed it was too soon to hand Real Madrid the title.
"We're favourites today, you can say that, of course," Ancelotti said after the win over Atletico.
"We've done very well, better than others, but we're focused on the next games because a drop in concentration can cost you dearly.
"We're doing well and we have to keep going, it's the only way to get close to winning as early as possible".
Five Premier League fixtures have been postponed due to outbreaks at a number of clubs this week amid fears of widespread disruption across European football.
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