Brazil forward Ronaldo has undergone medical examinations in a clinic after complaining of dizziness and headaches.

The Brazilian Football Confederation (CBF) said the 29-year-old, who had a dismal display in his team's 1-0 win over Croatia on Tuesday, felt dizzy yesterday, the team's had the day off.

It was added that nothing was found and he would be ready for training today.

"Ronaldo complained of feeling dizzy on Wednesday, July 14th, and was submitted to a medical check-up and additional examinations," said the CBF on its official website, confirming a briefing from a source to Reuters earlier on Thursday.

"No abnormality was found. Ronaldo is, therefore, in normal conditions for training."

The source said that Ronaldo had returned to the team base at 12 am (Irish time) after visiting a nearby clinic.

Ronaldo lumbered around the pitch against Croatia looking off the pace and struggling to control the simplest of passes in a performance described as "weird" by former Brazil striker Tostao.

Other critics said the world champions had effectively played with 10 men.

He was taken off to a chorus of jeers in the 69th minute and replaced by Robinho. However, coach Carlos Alberto Parreira said Ronaldo would keep his place in the starting line-up for Sunday's match against Australia in Munich.

The incident is bound to bring back memories of the 1998 final, when Ronaldo produced a similar dazed performance in the World Cup final against France which Brazil lost 3-0.

Afterwards, it was revealed that Ronaldo had been taken ill in the hotel hours before the match, some reports claiming that he had suffered a fit. The episode was never fully explained.

Ronaldo bounced back to finish as top scorer with eight goals at the 2002 World Cup finals including both in the 2-0 final win over Germany.

Before the Japan and South Korea finals, he had been sidelined for the best part of two years after undergoing two knee operations.

This season, however, has so far been an unhappy one for Ronaldo.

He was hindered by a series of nagging injuries and his relationship with the fans at his club Real Madrid deteriorated after he said he felt unwanted.

His last game for them was on April 8th, when he limped off after one hour with an injury to his right thigh.

During the preparations for the World Cup, he suffered from blisters on his feet during the 4-0 friendly win over New Zealand, which forced him to go off at halftime.

He then missed one day's training last week with a sinus infection.

He has become increasingly exasperated at suggestions he is overweight and became upset when Brazil President Luiz Inacio Lula da Silva joined the speculation, asking if he was fat during a video conference with the team last Thursday.

The President later sent a letter of apology.