Brazil remains optimistic over striker Ronaldinho's chances of being fit for Sunday's World Cup qualifier against Bolivia.

Ronaldinho missed Barcelona's opening match of the Spanish league season at the weekend with an ankle injury and despite being rested from Tuesday's training session, team doctor Jose Luis Runco said the forward was improving quickly.

"He's going to continue receiving treatment and we hope he will be able to train on Thursday," Runco said.

"He's got a good chance of playing."

Elsewhere, injury problems continued to mount for the world champions.

Central defender Juan was reported as doubtful while Gustavo Nery, reserve to Roberto Carlos at left-back, pulled out of the squad with a broken wrist.

Runco said that Bayer Leverkusen defender Juan, who is due to arrive later this week, had suffered a head injury during a Bundesliga match at the weekend.

Juan had won a place in the centre of the defence with his performances at the Copa America in Peru in July, where Brazil won the title.

Uncapped Leandro from Brazilian champions Cruzeiro was on Tuesday named as the replacement for Gustavo Nery, who plays for German champions Werder Bremen.

Brazil have already lost striker Luis Fabiano and midfielder Diego through injury.

Meanwhile, five players -- AC Milan trio Kaka, Cafu and Dida and Bayern Munich's Ze Roberto and Lucio -- were not selected in an apparent reprisal after they missed the so-called Peace Match away to Haiti two weeks ago.

"Obviously, in these circumstances and with everything that has happened, this game is going to be more complicated than the others," coach Carlos Alberto Parreira told reporters.

Brazil lead the South American World Cup qualifying group with 13 points from seven games. Bolivia, who have conceded 11 goals on their last two visits to Brazil, are bottom with six.