From ESPN:

Ginobili hurt his ankle early in the playoffs and a recent MRI exam revealed that a ligament in his heel is about five times the size of the one in his other heel, Popovich says.

Ginobili will have another MRI exam in three weeks, but Popovich said that "if it hasn't changed at all, I think he should definitely not play in the Olympics."

Check it - http://sports.espn.go.com/nba/news/story?id=3452488