The Selecao were held to a 0-0 stalemate at the Mane Garrincha Stadium in Brasilia, as South Africa put in a gutsy display against the hosts.
The Bracelona forward says the draw was as good as a defeat for his team, and believes things will only get tougher in their next games.
"We knew it wouldn't be a case of coming here and bringing home the gold," he said after the match.
"For us, the draw is a defeat. The team played to win, but we know our responsibility. We'll face more difficulties yet."
As one of the more experienced members in the side, the 24-year-old local superstar also feels the anxiety of playing in front of their own supporters affected their performance.
"We need to know how to overcome things but we'll stay calm and make things right as soon as possible so we can have a good game on Sunday [against Iraq]," he added.
"The first match is always the hardest because of the anxiety that marks the start of a competition, and I think that anxiety hurt us a little in the end."