Mercilessly cast as "greedy" and "missing" for failing to fire Brazil to victory in their Rio 2016 opener against South Africa, Neymar and his highly-touted teammates need a big response against Iraq on Sunday.

A 0-0 draw against a South African side reduced to 10 men for the final half hour on Thursday was met with a chorus of boos by a near 70,000 capacity crowd in Brasilia.

Brazil were expected to launch the Games in style as red hot favourites to land a first Olympic football gold thanks to the presence of Barcelona superstar Neymar.

However, he suffered the most severe backlash in the Brazilian press Friday after losing possession 27 times, more than double any other Brazilian player.

"Greedy Neymar becomes a problem in the Olympic team," said ESPN Brazil.

"Inexplicably, Brazil did everything contrary to what they rehearsed and preached for 17 days (in preparation)," added Rio newspaper O Globo. "Neymar was missing too."

However, Neymar, who still had Brazil's two best efforts brilliantly saved by Itumeleng Khune, defended his decision to act as more of a playmaker, comparing his role to that occupied by five-time World Player of the Year Lionel Messi at Barcelona.

"Sometimes you end up playing according to a certain player. It's like how Barcelona play. We play according Messi, he is the guy who plays more on the ball and we end up moving off the ball," he said.

"It's why we don't get bothered by touching the ball into Messi, that's what many people do not understand."

However, Brazil coach Rogerio Micale defended his star and captain, citing rustiness as Neymar hadn't been involved in competitive action since May 22 after skipping the Copa America in June.

"I think we have to see he is coming off a long holiday period and is regaining the pace of play," said Micale.

"He will grow a lot during the competition, I have great confidence in him."

Neymar didn't face the ire of the Brazilian press alone.

Manchester City's new £27 million ($36 million) signing Gabriel Jesus somehow managed to hit the post when presented with an open goal.

"I will not sleep tonight," admitted the 19-year-old.

Another slip-up against Iraq back in Brasilia is unimaginable for the hosts, but they will face a well-prepared and highly-motivated opponent who enjoyed the better of their opening 0-0 draw with Denmark.

In contrast to Brazil's short preparation time, Iraq have been in training camps across Europe for months in the build-up to the Games with the aim of surpassing their run to fourth at the Athens Games in 2004 when they beat a Portugal side containing Cristiano Ronaldo.

"For us it is an honour to be here," said Iraq coach Abdulghani Alghazali.

"In Brazil, we have earned the sympathy of the local people. Our next game, against them, will be very important for us."

Brazil aren't the only big nation in need of quick turnaround in fortunes on Sunday.

Two-time gold medallists Argentina face Algeria after suffering a 2-0 opening defeat to Portugal.

Defending champions Mexico opened with a 2-2 draw against Germany, but are expected to pile more misery on Fiji, who lost 8-0 to South Korea on Thursday. Germany also face the Koreans in Salvador.

Nigeria's Oghenekaro Etebo was the star of the opening round with four goals in a thrilling 5-4 win over Japan as the Africans shrugged off the jetlag with ease having arrived in the Amazonian city of Manaus, nearly 3,000km from Rio, just hours before kick-off.

Another win for the gold medal winners 20 years ago in Atlanta against Sweden will seal their place in the last eight.

Japan look to bounce back against Colombia, Denmark meet South Africa with both in search of their first win, whilst Honduras and Portugal face off with both well-placed after opening wins.

Neymar of Brazil talks to South African players. Photo: Reuters