The Selecao legend believes that the current side is weak at the back and could be shown up by Alberto Zaccheroni's men in Saturday's Confederations Cup opener
Selecao beat France 3-0 earlier this month in their last warm-up friendly before this summer's tournament, but previously struggled against the likes of England and Chile.
"From what I’ve seen Brazil are still a little too exposed for my liking and they allow teams too much space, especially for shots outside the box, which is what we saw in the games against England and France," Zico told Fifa.com.
"We’re not compact enough. England didn’t score twice from outside the area by chance, you know. That’s dangerous against a team with players who can shoot from distance, like [Keisuke] Honda, [Yasuhito] Endo and [Makoto] Hasebe.
"There’s every chance of this game being one of the toughest ever between the two sides, and that’s for two reasons.
"Firstly, the Japanese are getting stronger all the time, with more and more players in leagues like Germany, Italy, England and Russia. Secondly, Brazil are still looking for their best starting XI and the right formation.
"All in all, it should be a fascinating game."
Brazil meet Mexico in their second group game before taking on Italy on matchday 3.