Brazil, who are looking to win a record-extending sixth World Cup title, find themselves trailing European champions Spain, 2018 World Cup winners France and England in the bookmakers' odds for the June 11 to July 19 tournament in North America.
"We aren’t the big favourites," Casemiro told FIFA's media channel after Brazil arrived in the U.S. on Tuesday. "Of course, we’re in good shape; we’ve got a strong squad, with a mix of experience and young talent."
"Perhaps this time we’re a step behind, but we’re on our toes and that’s always a good thing. We want to go there in good shape and have a great World Cup.”
The 34-year-old said Brazil had had a "difficult cycle" in the build-up to the World Cup, with the Brazilian Football Confederation appointing Carlo Ancelotti as coach and naming a new president last year.
“It has been a difficult cycle with a change of manager, a change of president and a lot of turmoil," he added.
"We have only had one year working with the manager, who has excellent experience in football, but in reality we have only worked together for 40 days. I think we will go into the tournament in strong form.
"We have quality players, experienced players, energetic players and young players. I think we have a good mix for this competition."
Brazil will face Morocco, Haiti and Scotland in Group C.