Manchester United winger Nani was at the centre of allegations of a failed drugs test last week.
The News of the World says the Portugal star was dramatically ruled out of the World Cup on the eve of the finals with a collarbone injury.
But unfounded rumours began circulating back in Portugal that Nani has failed a random dope test.
The allegations grew to such an extent that the Portuguese Football Federation and the country's anti-doping authority were forced to put out strenuous denials.
Amandio de Carvalho, vice-president of the Portuguese Football Federation, said: "Nani was indeed injured. He fell badly in training and injured himself.
"There's no intention to hide anything. There's no need for an operation. He just needs time to recover. He can stay with us during the World Cup, if he wants."
Luis Horta, head of anti-doping in Portugal, added: "The rumours going around are without foundation.
"At least, with the controls carried out at the anti-doping authority in Portugal there exists no problem.
"Urine and blood samples were collected randomly. As far as we know, it all went well."