The tournament starts in Japan on Aug. 19, giving Yao just over two weeks to get ready.

"That's 50-50," Yao said Fiday. "Two weeks for me, I don't know. I'm going to try to get into my best shape in that time.

"If I really cannot get into the best shape, I better not go because the world championship is a very big thing for most of the (Chinese) players."

Yao, who had a cast removed from the foot last week, has been jogging in regular shoes for the first time since the injury. Now all he needs is his conditioning.

"Everything for me is very tiring right now," said Yao, who averaged 34 minutes in 57 games last season.

Even if he misses the world championships, Yao said he'll be ready to play by the time the Rockets open training camp.

"I still have plenty of time until October," he said. "That's good enough for me."

While he's behind in his offseason conditioning, Yao said he's still been able to work on his game this summer, breaking down film of himself and shooting jump shots.

He went through a similar rehab process last season, when he missed 21 games following toe surgery. He established himself as one of the league's top centers when he returned, averaging 26 points and 12 rebounds after the NBA All-Star break. He topped 30 points six times in March.

"I always want to do more, whatever will make me better," said Yao, who averaged 22 points and 10 rebounds last season. "It's pretty similar to my injury in the season. I can do some things on the court right now ¡ª not the post moves yet, but pretty soon, I think."

Yao has set two statistical goals for next season: more minutes and a higher field-goal percentage. He shot 52% from the field last season, but his goal is 55%.

"I hope I can stay more minutes on the court. I believe that would help the team," Yao said. "My field-goal shooting needs to go up a little bit.

"I have a lot of work. I need to work on my skills, I need to work on my shot ¡ª everything."