Doc said in the article that he didn't want Shaq back out there until there was a practice and that Shaq went through it. Team didn't practice Saturday, so honestly Shaq's chances at playing in Game 4 ended there.
If the C's sweep tomorrow, Shaq has a whole week to prove he should play in Game 1 vs probably the Heat. I personally like his chances, but that's all Shaq has at this point; a chance, not a guarantee.