Since the Celtics won't elaborate, we are forced to speculate. Some suspect mono. If that were the diagnosis, would the doctors let him hang around other players? Others suspect a heart condition. Green refuted this diagnosis on Tuesday.
Let's read into Danny's quote, "It depends on your perspective." If Green has a serious but non-life threatening condition, his long term perspective might be one of relief. But if that condition will keep him off the court, the short term perspective is one of frustration.