The report (in Chinese) says that Yao turned down the role because director Brett Ratner asked him to play a bad guy, which would ruin the image of a good guy that he's worked to cultivate through the years.
You might be thinking, as we are, how Yao could possibly be a villain. First of all, bad guys, no matter how bad-ass they are and no matter how many crooked cops they have under their control, have to keep a low profile. This is hard to do when you're over seven feet tall. When the police make you do the line-up with other suspects, you'll stick out like a sore thumb.
Secondly, how could someone that clumsy possibly kick enough ass to be a master villain. We know what you're thinking -- Yao has skills, how could you say he's clumsy? What we mean is that he's not quite coordinated in the way that say, Jackie Chan is. It turns out that the reason, as reported both in the Chinese article and in Rotten Tomatoes, is that Ratner wanted to recreate a scene from the 1978 Bruce Lee film Game of Death where Lee fights Kareem Abdul-Jabbar.
Some of you might have hoped that we would be spared another installment of the series because Chris Tucker wanted a lot of money as well as final cut rights, but it seems from recent reports that they somehow managed to find a solution, because the movie is in production and will be released some time next year.
Image from NBADraft.net.

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