Vinicius Junior must repeat a COVID-19 test after an apparently anomalous result, Real Madrid head coach Zinedine Zidane has revealed.
Zidane was speaking ahead of his team's LaLiga match against Deportivo Alaves on Friday, where Vinicius' participation is now in doubt after a test "went badly".
The 19-year-old sat out training on Thursday and must wait to find out if he will be available to face Alaves.
"The doctors informed me that the test went badly and that we need to repeat it," said Zidane, who will be without Luka Jovic after the forward was forced to self-isolate due to coming into contact with a friend who contracted COVID-19.
When he was asked to clarify whether "badly" might mean Vinicius had tested positive for coronavirus, he replied: "Sometimes there are errors. That can happen.
"Whenever something like that happens, the player can't train. I hope it's nothing and that he can be with us for Friday's game.
"We'll have his results this afternoon."
Even if Vinicius is forced to sit out, Eden Hazard will be available as Madrid seek a victory that would give them a four-point advantage over Barcelona with three games remaining.
The Belgium playmaker was absent from the back-to-back 1-0 wins over Getafe and Athletic Bilbao and has had his debut season in the Spanish capital ruined by a broken foot.
"It is not a relapse and he has trained with us normally," Zidane said.
"I hope he will be with us in the four remaining games and then in the Champions League.
"He wants to be with us and he is not afraid, but it is the third relapse and it bothers him a little.
"There are people here who know much more than me and the image [X-ray] comes out clean, it is perfect, but the discomfort is normal after a game or strong training.
"He is not afraid and wants to help the team and tomorrow he will be with us "
Marcelo faces a scan on an unspecified complaint, but Raphael Varane is set to return at centre-back after recovering from concussion.
"We haven't won anything," Zidane said, when confronted with his team's strong position heading into the final stretch.
"Four games are remaining and tomorrow is another final.
"I am sorry to repeat myself, but there is no other choice. What we want is to continue with what we are doing."