Chelsea midfielder Willian, who scored 44 times in 11 appearances for the Blues last term, could play a part in Brazil's opening game against Switzerland on Sunday.
Writing in a column for The Mirror, Carlos said that Willian is "right up there" with the best at the tournament and could surprise with his ability.
"Neymar is going to be marvellous in Russia and win the trophy for us," the 45-year-old said. "But you know who else is going to have a big World Cup? Willian. People talk about [Lionel] Messi, [Cristiano] Ronaldo, Robert Lewandowski and Neymar, but for me, Willian is right up there.
"He's in really good form and always takes responsibility on the pitch. He's a quiet guy who keeps to himself, but he's going to surprise a lot of people this summer.
"Willian is going to be the best player at the tournament, alongside Neymar. He knows how important he is to this team and I want to see him start with a bang against Switzerland tonight."
Willian has scored eight times in 57 appearances for Brazil.