"At no stage has our player been diagnosed with an alleged anxiety attack and these reports are therefore completely false," Real said in a club statement.

"Thibaut Courtois has been diagnosed and treated for an acute case of gastroenteritis with dehydration and electrolyte imbalance, which meant that he was unable to complete Tuesday night's game against Brugge.

"The player is currently responding well to treatment."

Courtois' form has again come under scrutiny this season due to several mistakes which have cost goals.

The 27-year-old has conceded 81 goals in 58 games since joining Real from Chelsea in August 2018, and was the main topic of questioning for Zidane ahead of Saturday's top-of-the-table LaLiga clash with second-placed Granada.

"It is what it is, and he knows that," Zidane said when asked about the fans' whistles being directed at Courtois in midweek.

"He is strong, he knows he can turn the situation around. The first half the other day is about everyone, you can't keep going over it.

"Here there are no undroppable players, not Courtois or anybody.

"The people can talk about Courtois' errors but for three games in a row, he kept a clean sheet and that was him.

"I can always speak with players. I didn't speak with him specifically about the whistles against Brugge.

"We know what we did and we will keep looking forward."

Gareth Bale and James Rodriguez should return to the squad after missing the midweek game.

But a thigh strain rules out Marcelo, and Real are short of defenders with Ferland Mendy and Nacho also sidelined by injuries.

Real are top after seven games, one point ahead of Granada and Atletico Madrid, but have struggled in Europe and are without a win in the Champions League.

"We are not as bad as people outside are saying but this is Real Madrid," Zidane said.

"It won't change what people say. We are focused on what we can do on the field.

"We have a game now to stay first at the end of the game."

Promoted Granada have been the surprise package in Spain this season with 14 points from their opening seven games.

Granada's win include a 3-0 victory at Espanyol and a 2-0 home success over Barcelona.

Former Tottenham and Valencia striker Roberto Soldado, who began his career at Real Madrid, could miss out with a thigh problem.

Adrian Ramos or Carlos Fernandez stand by to deputise for Soldado, while midfielder Eteki has been ruled out with an ankle problem.

"Real Madrid is the winner of several Champions Leagues in recent years, it is a top team," Granada manager Diego Martinez said at his pre-match press conference.

"It has taken us a lot to get here and we are a good team.

"But we belong to different universes and in 90 minutes we will try to minimise that.

"We want to be competitive and to show the best of ourselves. That is the path we are going to follow to try to win at the Bernabeu."