There are a lot of anaylsis going on regard of what is wrong with Wang. This is the version I believe Wang's problem coming from as follows,
According to keeping up with Jones blog,
Bruney believes Wang's troubles stem from not yet trusting his right (push-off) foot. Bruney says he was doing the same thing during his rehab, and his velocity was down and his stuff was off. He worked his way through it -- and has been great out of the pen -- which is what he says Wang has to do.
Please keep these words in mind and combine them with this video from MLB Network, I believe this is Wang's problem.
I am not a pitching coach and I don't know how you let Wang trust his right foot again. Based on what I hear from Girardi during his pre-game interview, I believe Yankees coaching staff know what Wang's problem is. The problem I have is why they don't recognize this problem during spring training and collect it under less pressure situation, when you consider Wang doesn't have a good spring training and he doesn't have his sinker working.