It's stress fracture, and Yao said if he needs to undergo surgery, he'll retire. There is still a fair chance that this can be healed on its own with rehab. There is a SLIM chance that Yao is going to bite the bullet, to go through the rigorous rehab once again and come back to court.
The big fella is a classy guy, and fun to watch when he's on it. Although I have always wanted him to do more and better, he's the one who can proudly say he did everything he could and some more.
I am not ready to write a long piece of appreciation nonsense yet, still hoping that he could somehow come back, even as a situational player with very limited supporting role.
What a freaking great way to start the day. Sigh.