SHENYANG, China (AP) Dunga is yet to decide on Brazil's starting 11 for the match against New Zealand, and defender Thiago Silva could return to action after practicing for the first time on Friday.
Thiago Silva, one of Brazil's two overage players along with Ronaldinho, is recovering from a right leg muscle injury and may be available for Sunday's match at Shenyang Olympic Stadium.
"It's still too early to say," Dunga said. "We will have to see how he progresses and if he is fit I will decide whether he will get to start."
Silva had been undergoing treatment and taking part in physical conditioning drills until Friday's practice session.
Silva's replacement in Brazil's 1-0 win against Belgium on Thursday was Bayern Munich's Breno, who played well from the beginning.
"There are no regular starters in Brazil's team," Dunga said. "Every player has to be ready to come in when needed, be it for 90 minutes, five minutes or one minute."
Dunga made three substitutions against Belgium and was satisfied with the results. Thiago Neves replaced Anderson and Jo replaced Alexandre Pato in the 75th minute, while Ramires substituted Diego in the 85th.
Brazil's winning goal by Hernanes came just four minutes after Dunga made the first two changes.
"I made the substitution because of the heat, and the team responded well," Dunga said. "It gave us more rhythm and the goal came quickly."
Belgium had been a man down since defender Vincent Kompany was ejected in the 72nd minute.
After facing New Zealand on Sunday, Brazil will travel to Qinhuangdao for its final group-stage match against host China on Aug. 13.
The top two teams in each of the four groups will advance to the quarterfinals. Brazil leads Group C with three points, while China and New Zealand have one each after drawing their opener 1-1 on Thursday. Belgium has no points after the opening round.
Each nation is allowed to use three players older than 23, but Dunga has only Thiago Silva and Ronaldinho as coverage players because stars such as Kaka and Robinho were not released by their clubs.
The Olympic football tournament began one day before Friday's opening ceremony in Beijing to accommodate its lengthy schedule.
Brazil has never won the Olympic gold medal. It won the silver twice, at the 1984 Los Angeles Games and at the 1988 Seoul Olympics, and bronze at the 1996 Atlanta Games.