The Brazil defender gives Ranieri the credit for turning Roma's season around and looks ahead to the World Cup.
"Since Ranieri arrived we have found the right motivation," said the defender.
"After so many years under Luciano Spalletti, who I consider one of the best tacticians in the world, perhaps we needed to be shaken up a bit. We were tired psychologically.
"The Coach arrived without a big splash and was able to wait for the right moment to make tactical changes."