"The fact that we've all been surprised by their results in these first two matches, that doesn't mean that they're not the same Spain as before," said Gonzalez, who scored the decisive goal in Chile's 1-0 defeat of Switzerland on Monday.
"They're the same players. We all know perfectly well the quality and the individuals that they have, and they're perfectly capable of making things difficult for us."
Spain surprisingly lost their opening match against Switzerland before beating Honduras on Monday.
They need to beat Chile in Friday's final Group H clash to be guaranteed a place in the second stage. Chile, with two wins from two matches, need only a draw.
Gonzalez, who has figured as a second half substitute in both Chile's outings so far, said he expected the game in Pretoria to be an open encounter - in stark contrast to Monday's match against a Swiss side who concentrated on defence.
"I think this match is going to be something special, because they have to give it their all and we have the option of either winning or drawing," he said. "It's going to be a different kind of game. They're going to have to come out an attack and logically we'll try to impose our style of play."
Gonzalez described scoring in the World Cup as "the best moment of my life" and said it was all the more enjoyable knowing his family were there to share it. He was born in South Africa and still has family here.
"My siblings, my father, my cousins, my family, they were all in the stadium, so I'm happy," he said. "It was the most important moment of my career, so knowing that I had my family here supporting me."
