You don't seem to grasp this, but the real risk is him having another good season and then completely walking. The fact you keep mentioning Zuccarello and Brassard in the same wavelength further indicates you don't get it. Zuccarello's 40 assists last seasons are 7 points shy of Brassard's career best points in a season. Add in that Zucc is the better checker, the harder worker, the superior defensive player, and these two aren't too close.
If Zucc puts up similar numbers to last season, he isn't getting the $4.5 you mentioned, it's more like $5.5. But the real risk isn't the funds, it's him having a good season, which he likely will, and then walking altogether.
All I'm saying is let's see him do it again before we give him a long term contract. If Zucc scores 70+ points and gets a ridiculous contract, I'll eat crow. My point is that the likelihood of that is low.