The Toronto Maple Leafs can not afford to lose Nylander. He was the best played they’d drafted since Wendel Clark at least, (and probably he’s way better) before they got lucky and also landed Auston Matthews and Mitch Marner.
Any credible hockey analyst can tell you that Marner and Nylander are pretty much at the exact same level of skill and effectiveness. There is no statistical (read: non biased) reason to think Marner is any better than Nylander.
Nylander is irreplaceable. He is going to be one of the best players in Toronto Maple Leafs history, he only missed the top ten in scoring last year because his totals were artificially suppressed with a lack of ice time, and power-play time, and he is a legitimate elite player.