Brazil midfielder Ze Roberto has warned compatriot Luiz Felipe Scolari of the threat of France playmaker Zinedine Zidane ahead of Portugal's World Cup semi-final showdown with Les Bleus.

Scolari leads Portugal into battle on Wednesday against the conquerors of Brazil, and Ze Roberto believes he will assign a player to man-mark Zidane.

"Because of his form with Real Madrid, we knew that he could make the difference along with (Thierry) Henry," said the ex-Bayern Munich midfielder.

"At the beginning of the quarter-final, he already had too much freedom. And thanks to that freedom, Zidane built up plays and became the brain of the French team.

"Scolari will put a player on him because, if not, he'll make the difference again."

The 31-year-old admitted that his country's shock exit was down to a lack of team unity.

"The unity we forged off the pitch was not on the pitch," he continued.

"After 10 minutes of play, our spark and enthusiasm slipped. We tried again in the last few minutes, but it was too late."