"Maybe it was a marketing move at first," Kaka told SporTV. "But today the truth is that he is fundamental. He is a player that in the last games was very decisive, with passes and goals." Despite missing a deadline from Major League Soccer last Friday,
Milan was still trying to make Beckham's loan to the Italian club permanent. Beckham's three-month loan from the Los Angeles Galaxy ends on March 8.
"I wish Milan can reach a deal to acquire him permanently because he is a player who can help us now and in the next seasons," Kaka said.
He also praised fellow Brazilian and club team-mate Ronaldinho.
"Ronaldinho remains a spectacular player," Kaka said. "We play and practice with him every day and we see that his quality is unique, it's impressive. Today he is in a much more experienced phase in his career.
Now he doesn't try to charge forward every time he gets the ball, he knows how to balance his game."
Kaka reiterated that his desire to make history at AC Milan was key in his decision to reject the record offer from Manchester City last month.
"What I represent for Milan and what I have achieved and still want to achieve with Milan was a big factor in my decision."
He said the demonstrations from fans asking him to stay also played a role, especially during the match between Milan and Fiorentina in the midst of the negotiations.
"Everything was very moving," Kaka said. "From the time I got to the stadium to the time I entered the filed. During the entire match it was very moving, I couldn't focus."
Kaka said he felt an obligation to hear the Manchester City offer.
"Milan doesn't usually sell players," he said. "When the club opened the possibility, out of respect I needed to at least hear what they had to offer."
On Tuesday, the Estado de S. Paulo newspaper reported that Kaka told authorities last year that he donated €200 000 to his church in Brazil, the evangelical Reborn in Christ Church.
Kaka was questioned by police at the time for his alleged link with the church leaders, who have pleaded guilty to money smuggling in the United States.
He has always denied any wrongdoing and has never been charged