The Oranje have impressed so far after progressing as Group B winners with victory in all three games, including a shock 5-1 dismantling of Spain in their opening encounter.
However, Robben, who has scored three times in Brazil so far, insists that the Dutch should not dwell on their successes to date when they come up against Miguel Herrera's men on Sunday.
"They are dangerous opponents," the Bayern Munich attacker told the Times of India.
"Especially when the match is being played in Brazil, a country more familiar to them. They are fearless opponents and proved it against Brazil in their group league match [a 0-0 draw].
"It's really been an unbelievable start for us. Before the World Cup, if you had said to me that we shall win all the three matches of the group, I would have not have believed you! But that's football and we did almost everything right to qualify for the round of 16."
Robben, who missed a golden opportunity when one-on-one with Iker Casillas in the final of the 2010 World Cup which the Dutch lost 1-0 to Spain, also stressed that he was pleased to have gone some way to making amends in this edition of the tournament.
"This was a new beginning," he said of the 5-1 win over la Roja on June 13.
"We were not playing them in the final of the tournament, rather it was our first match. And we were behind them.
"Then we played a second half that was almost like a dream performance. As if, we could do whatever we wanted to. That was the most pleasing part of that performance.
"It was satisfying. My goal gave us the lead and we were unstoppable after that, scoring goals at will almost. Scoring five goals against the world champions is something we shall never be able to forget."