The 22-year-old is aware that the Selecao must improve from their performance against Croatia and says he is constantly on his toes to prevent being dropped from the side
Oscar believes that Brazil must improve if they are to fulfil the hopes of a nation and win the World Cup on home soil.
The Chelsea playmaker's late goal added to a Neymar double as the hosts recovered from falling 1-0 behind to triumph 3-1 against Croatia in their opening Group A game on Thursday.
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That moment proved crucial as Neymar put his side ahead for the first time in the game and Oscar, who was delighted to come away with the points, is aware that there is room for improvement versus Mexico on Tuesday.
"The first game is always difficult, especially after conceding an early goal," he told reporters on Saturday. "But it was very good. Although we conceded the early goal, we played well and found a response.
"The next game will be hard again. Every game for us is final. We have to fix things and we have to think about the next game."
Oscar is a key part of the Selecao set-up but, although he acknowledges that Luiz Felipe Scolari has faith in him, the Chelsea playmaker is well aware of quality replacements waiting in the wings should he underperform.
"Felipao has trusted me for a long time," he added. "It's not a new thing. This trust was proved on the pitch. He told the media this and he has always believed in me.
"Not only has Willian been training well, but Ramires has as well. Hernanes too. There are no regular starters or reserves on the national team.
"If I play badly, someone comes in, scores a goal and stays. I have to prove every match by putting in another good performance."
Brazil are back in action on Tuesday against Mexico before facing Cameroon in the final group game on June 23, six days later.