Without detailing the cap dynamics of various scenarios, the Penguins need to decide — and likely already have — whether Crosby may return in the regular season.
If that possibility still exists, Shero will have very little cap space to maneuver. Any trade that adds substantial salary to the roster will have to be accompanied by a similar cap hit heading the other way.
If Crosby is expected to miss the rest of the regular season, the Penguins will be able to replace most of his $8.7 million cap hit with replacement players.
The whole article is worth the read. It is here.
As Mike points out, the Penguins have most likely already decided on Crosby's status, or at least have a good idea about it. So in about two weeks we'll probably have a better understanding of whether or not Crosby is coming back this season.