Real Madrid boss Jose Mourinho believes Kaka has not lived up to his billing since moving to the Bernabeu in 2009, suggesting a return to AC Milan may allow the Brazilian to rediscover his best form.
Kaka, 30, was close to securing a loan deal with the Italian club in the January window but contract negotiations between Milan and Real broke down, meaning he will see the season out in Spain.
The midfielder has failed to assert himself in Los Blancos' first team and requested a transfer to search for regular football.
Mourinho has hinted that Kaka is likely to move to Milan in the summer, insisting the World Cup winner should not be judged on his last three years.
"At Real Madrid we never saw the real Kaka," Mourinho told Rai. "He must be happy and Milan could be a good solution, but he is a Real Madrid player."
Speaking on his own future, Mourinho failed to rule out a return to former club Inter Milan amid much speculation about a rift between the Portuguese manager and his Real players.
"Now I am 50, I could still coach for at least 20 more years and many things can happen," he said. "Maybe [I could] come back to Inter, why not?"
Real face a tough Champions League round of 16 tie with Manchester United and while his side could put themselves into strong contention for the title by overcoming the Premier League leaders, Mourinho believes Juventus are the team to beat.
"Juventus are a top team," he said. "It's easy for them to say that they are not the team to beat in the Champions League.
"A lot of people say that the favourite teams are Real Madrid, Man United and Barcelona, I say that Borussia Dortmund, Bayern and Juventus can win the Champions League."