From the Taiwan News:

Taiwan-born New York Yankees starter Wang Chien-ming (王建民) returned to Taiwan yesterday morning and pronounced his right foot injury that forced him to miss the last four months of the season completely healed. ...

Asked whether he will pitch for Taiwan in the 2009 World Baseball Classic, Wang said Yankees general manager Brian Cashman believed the pitcher will not be able to regain his top form in time for the international competition next March, and therefore did not want him to participate.

Via Ben.