Louis van Gaal's side was given a tough assignment in Group B in Friday's draw, with a repeat of the 2010 final seeing the Dutch tackle Spain before meetings with Australia and Chile.
While many were drawn to the tie of the round against Spain, Gullit claims that Chile will be every bit as tough a prospect as will Vicente del Bosque's men.
"After the match against Spain we cannot think we have already played the hardest opponent," the 51-year-old told reporters. "Please do not underestimate Chile. They are a very strong team.
"They have got the advantage of playing on their home continent, and South American teams always play better over there than they do somewwere else. It's different against Australia. Oranje must win that match, that's for sure."
After the Spain clash in Fortaleza on June 13, Van Gaal will take his men to Porto Alegre for their match-up with the Socceroos. The all-important Chile fixture takes place in Sao Paulo on June 23.
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