Obviously they're aware of the issue, but that doesn't mean there aren't ways to play down the extend of an injury, to delay surgery, and so on.
Zollins' issues are acknowledged first and foremost by none other than himself and the FO, by the mere fact that he signed a contract lightly guaranteed... something in the ballpark of 10 million dollars (I think it's 7 per for 3 years total)... you're talking a quarter of a billion guaranteed over 5 years (for the Bulls). That's an entirely different story.