The Selecao have progressed to the quarter-final stages after defeating Chile 3-2 on penalties in Belo Horizonte on Saturday after the sides were locked on 1-1 after extra time.
Both Fred and Oscar started the last-16 clash with la Roja but have been under scrutiny in their homeland for their displays, something Kaka does not believe is justified.
"We should remember that Fred had a very good Confederations Cup last year," the 32-year-old said in an interview with the Times of India.
"He has a lot to give to the team. He's had a slow start but picked up and can become one of Brazil's big players as the tournament goes on.
"[Oscar] has done very well," he continued.
"Before the start of the tournament there was a lot of debate in Brazil about whether Oscar should start, but he played really well against Croatia and scored an important goal.
"He has shown he deserves to be in the starting XI for Brazil. He is always willing to help the team, not just do his own job."Kaka, a World Cup winner in 2002, also believes that that the Verde-Amarela are well positioned to be successful, with South American teams potentially better rested than their European counterparts.
"The European teams are coming on the back of a long and hard season," he mused when asked why the likes of Italy and England had struggled.
"Some of the South American players are only halfway through their seasons. Also the climate may have played a part.
"That, too, may have had an effect. But don't forget Germany and Holland, who have had a full European season, have played well and are through.
"This Brazilian team works hard and is talented, so that should be enough for them to progress."
Finally, the midfielder reflected on not being selected by Luiz Felipe Scolari for the tournament in Brazil.
"I did my best to make the squad, but I respect the manager's decision," he said.