Both can fit if the big three aren't too greedy, which isn't seeming like the case at the moment for Nylander and Marner based on their agents. Still holding out hope Matthews signs a team friendly deal, but based on how he's playing, it could be team friendly and still huge.
As much as I love Jake, who is criminally underrated around here, I would have to go with Nylander. Too much high end skill and too young to let go.
However, choosing between Zaitsev and Gardiner, who shouldn't cost that much more, is pretty easy. (I do have a soft spot for Z because he chose Toronto when we still sucked, so like to see it work out for him.)