Well it's nice to see somebody finally lay it out.
The key passage:
It all figures to come to a head by the end of next month. Unless Song gets injured again during the rehab assignment, a predicament that would stop the 30-day clock and rewind it to the beginning, the Phillies will have to make a decision on him by July 29.
By then, there will be less than 90 days left in the season. But according to a league source, the Phillies would be allowed to retain Song as long as they kept him on the roster for the duration of the season and however many days spill over into next year to reach the 90-day mark.
So, that's a pretty low bar. If he's not up to it they could still hide him for most of August, use the extra roster spot on a more usable pitcher in September, and then he'd be free of the Rule 5 stipulations by May 1 of next year.