Brazil, captained by Ronaldinho, struggled to a 1-0 win over nine-man Belgium in their opening match at the Olympic Games' soccer tournament on Thursday.
Midfielder Hernanes cut inside his marker and fired between Logan Bailly and the near post in the 78th minute to get Brazil off to a winning start in their quest to win a first gold in Olympic soccer.
Defender Vincent Kompany was sent off for a second bookable offence when he fouled Diego in the 73rd minute and the physical Belgians also had Marouane Fellaini dismissed in the 88th minute, also for a second bookable offence, in the Group C game.
Ronaldinho, who joined AC Milan from Barcelona last month, has been included by Brazil as one of their three permitted overage players in the under-23 tournament and handed the captain's armband.
Plagued by injuries and fitness problems with Barcelona last year, Ronaldinho looked lively when he got the ball, producing plenty of shimmies, flicks and dribbles, but was often left isolated and frustrated on the left flank.
He was greeted by rapturous applause when he came on the field and a huge cheer went up every time his face was beamed onto the big screens around the Shenyang Olympic stadium.
With a line-up also including Diego, Anderson, Alexandre Pato and Lucas, Brazil looked the much stronger team on paper but were frustrated for long periods in stifling heat and humidity.
Ronaldinho's first attempt on goal was a 30-metre free kick which was deflected over. He tried again from a similar position five minutes later but this time his effort went straight into Bailly's arms.
Alexandre Pato created an excellent opening after the restart when he latched onto Diego's pass and cut inside his marker but then shot wide of the post.