We know the Islander's coach. Could Barzal put up another 20+ points per year somewhere else? I think it's plausible.
Maybe, but he's not that on the Isles. And if Trotz's system puts that much of a value on D and gimps production, would it be better to bump Nelson and Pageau up a spot, get a haul for Barzal, and invest that cap elsewhere on the team?
I'm not trying to bag on Barzal here. I've seen guys like Yzerman, Fedorov, Zetterberg, and Datsyuk play under Bowman and Babcock. Those centers were great defensively and still got their points in those systems. If you're looking at spending $8+ million on a guy, I think you want him to get his points and be fit the system.