JOHANNESBURG (AP) — Kaka says he's ready for one of the biggest challenges in sports: leading Brazil at a World Cup.

Kaka enters the tournament as Brazil's biggest star, but he also arrives bothered by injuries. The brilliant playmaker, however, is confident he will be in good physical condition when the World Cup begins for the five-time champions on June 15 against North Korea.

"I am getting better every day," Kaka said. "The injury does not bother me anymore. I've been doing everything planned so far, and by the time we play the opener I will be in great condition."

Kaka is coming off an injury-plagued season that kept him from being at his best with Real Madrid. He had groin and thigh problems that kept him sidelined for 45 days at one point, unable to perform like the FIFA player of the year he was in 2007.

Brazil doctors said the groin problem is not an issue anymore, and that the left thigh ailment should not keep Kaka from starting for Brazil in the team's opener.

"I was worried at first," Kaka said. "It was very limiting, but now I'm being able to move around much better. I'm going through intense treatment, and with 10 days left until the opener I will be fine."

Kaka has been practicing normally with the rest of the Brazilian players since the team arrived in South Africa on May 27, but continues to receive separate treatment even when the other players get a break.

He played 45 minutes in Brazil's 3-0 warmup win over Zimbabwe in Harare on Wednesday and said he felt fine.

"It wasn't my best match with Brazil, but it was very positive," the 28-year-old Kaka said. "I was able to do a lot on the field without any problems."

It was his first match in more than a month, and coach Dunga also was pleased with what he saw.

"He is progressing, and the tendency is for him to keep improving," Dunga said.

Kaka was already a top player with Brazil at the 2006 World Cup, but at the time he shared much of the spotlight with Ronaldinho, Ronaldo, Roberto Carlos and Adriano. Now, few players are attracting similar attention to what Kaka draws.

Wearing Brazil's famed No. 10 jersey, Kaka knows all eyes will be on him this time.

"I'm ready to be one of the team's leaders, I'm ready to take this responsibility," Kaka said. "I've always accepted this responsibility."

Kaka also was a member of the 2002 team that won the World Cup in South Korea and Japan, but he played less than 25 minutes in that tournament.

One of Adidas' high profile players, Kaka also downplayed complaints from teammates about the ball being used in this month's tournament, saying such criticism is normal before every World Cup.

"I'm not going to criticize the World Cup ball," he said. "I always hear players complain about the ball in every competition. People were complaining a lot in the first week, but then everyone starts adapting to it and things start changing."

Players from Brazil and other nations complained about the ball, some even comparing it to those bought at supermarkets.

"It's a new ball, and everything new causes an impression," he said. "There have been some complaints now, but maybe during the World Cup players will start saying different things."