The 31-year-old was used predominantly as a substitute or in less important games under Jose Mourinho in 2012-13 and was left out of Luiz Felipe Scolari's victorious Confederations Cup side as a result.
However, under former AC Milan boss Carlo Ancelotti he hopes to get more game-time in order to impress at the Santiago Bernabeu and make the Selecao squad next summer.
"My challenge for this season is to play more regularly," Kaka told Adidas. "I want to be physically fit and then if I do well for my club I can get back in the national team.
"I want to play in the World Cup next summer. Carlo is an open coach who is helping me a lot. Personally, it’s great to train with him."
Kaka has made 87 appearances for Brazil since his debut in 2002 though, since joining the Blancos in 2009, he has struggled to find the form which saw him win the Ballon d'Or while at San Siro.