Despite the tournament being hosted in their homeland, the Paris Saint-Germain centre-back thinks that the Brazil squad is not as good as the 2010 World Cup winners.
"Even though we beat them 3-0 in the Confederations Cup final, we don't believe we are better than Spain," Silva told Le Equipe.
"But Brazil is still Brazil, we are always strong, especially because we are at home. Every team will come to us with the hope of knocking us out. We need to work hard to make our objective, which is to win the World Cup, a reality."
The draw for the competition is on Friday.