France midfielder Lassana Diarra was ruled out of the World Cup because of a genetic red-blood cell disorder, according to his Spanish club Real Madrid.

Diarra returned home after missing the last three days of training in the French Alpine resort of Tignes, and Domenech has yet to decide whether to call up a replacement ahead of Wednesday's home friendly against Costa Rica.

"He wasn't ready physically, he was really exhausted. The illness was triggered off by the altitude, he had predispositions that we couldn't detect in advance," Domenech said on Sunday. "He needs a good 15 days rest to fully recover, and he will recover, that's for sure.

"It won't have any bearing on the rest of his career, but he's not fit to play in a World Cup."

Diarra's illness was apparently triggered off when the France team travelled to the foot of La Grande Motte glacier, where it slept in a restaurant at an altitude of around 3,000 meters in a team-bonding exercise on Wednesday night. Domenech was asked on French television on Sunday if he aware that Diarra had a medical condition.

"No. Apparently neither was the (France team) doctor. There's a medical confidentiality that is kept by the clubs, by the players," Domenech told the weekly football show Telefoot. "We didn't know. No one knew it was altitude that could trigger it off because, as far as I know, it can be triggered off by other (things)."

Real Madrid said in a statement on its website that Diarra is "now resting at home following medical advice due to asthenic syndrome secondary to a sickle-cell anemia that will be subjected to a hematological study in Lyon Hospital."

Sickle-cell anemia is a genetic blood disorder where red blood cells form an abnormal and rigid, sickle shape.

Diarra trained with the France team at the same resort two years ago before the European Championship, but Domenech said the player "had no problems" at that time.

"Of course it's a blow when you lose a player. It's even harder because it wasn't a choice, it's destiny," Domenech added. "It's tough for him because I know how much effort he had put into this World Cup. He was one of the driving forces of this team in terms of the way he played and his attitude."

France striker Djibril Cisse said the players were upset to hear about Diarra's illness.

"We are all behind him, and my teammates have asked me to pass this message on: that whatever happens he will always be part of this adventure," Cisse said.

Cisse can sympathise because he broke his leg on the eve of the 2006 World Cup in a friendly match against China, and was not selected for the European Championship because Domenech dropped him.

"I've gone through the same thing twice, once through injury and once when the coach made a decision, so I know what it's like to do all the preparations and not go to the tournament," Cisse said on Sunday on Telefoot.

Domenech decided not to risk taking Diarra to South Africa after the player missed training on Saturday evening.

On Saturday, the France team was vague about the nature of Diarra's illness, saying just that he first felt "intestinal pains" on Wednesday when the squad travelled to the foot of La Grande Motte glacier, where it slept in a restaurant located at an altitude of around 3,000 metres in a team-bonding exercise. According to the team, Diarra was not able to shake off the pains.

"He was complaining about his stomach up there, but we couldn't imagine that it would be this," Cisse said.

Arsenal defender Gael Clichy saw Diarra briefly before he left the team.

"I woke up at about six o'clock in the morning and I saw he was getting dressed. I thought he was going out for a walk... he said he wasn't well and had to go to hospital," Clichy said. "He's an important player for us, but I think it's something which can bring the squad closer together."

The France team allows no media access to the medical staff, and the only additional detail given was that Diarra needed to rest for "an indefinite period", France press officer Francois Manardo said on Saturday.

Diarra has played 27 times for France since making his debut just over three years ago, and was a regular in the qualifiers in a holding midfield role alongside Jeremy Toulalan.

Domenech, who must now rethink his plans as to what formation to play, has until June 1 to name his 23 players for the World Cup.

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