Kapanen can and does PK. That says a bit about his defensive solidity, and as he is a good skater at the same time, at least Babcock could give him a regular 4th line shift until openings for him came about higher up in the lineup.
Part of Sprong's troubles is that he doesn't have something like that to fall back on, and at least some of Sullivan's hard line approach must be to try and force him to develop habits that does not make him a liability when he isn't in a position to be a scorer. Everyone can hunker down in their respective bunkers and think that is wrong or right, its probably a bit of that and some of the other, but certainly Sullivan would not be the first coach with that mindset. And Sprong has not helped himself on that account - less so in the most recent showings.