Barcelona star Neymar failed to provide the flying start Brazil wanted in their quest for a maiden football gold medal as the hosts were held 0-0 by 10-man South Africa in their Olympic opener.
Neymar is by far the biggest name taking part in the football competition and has been tasked with restoring pride to Brazilian football after a catastrophic 7-1 defeat to Germany on home soil at the 2014 World Cup.
Portugal beat Arg 2-0
Portugal's stunning summer after winning Euro 2016 could get even more golden as they saw off Argentina 2-0 to the delight of the Brazilian crowd in Rio. Both sides are looking to the future with lionel Messi having announced his international retirement with Argentina after three final losses and Portuguese hero Cristiano Ronaldo now 31.
Gonzalo Paciencia's low drive put Portugal ahead before a horrible error from Argentina goalkeeper Geronimo Rulli allowed Pite's long-range effort to sneak between his legs to secure the three points six minutes from time.
In other matches, Honduras beat Algeria 3-2 in the other Group D game. World champions Germany played out a thrilling 2-2 draw with 2012 gold medallists Mexico.