I don't know if Toronto will be able to return a 1B or 2A center for Nylander. Depending on your definition there really aren't that many of those guys out there, and the teams that have them probably aren't super eager to give them up. It's also difficult to base any Nylander trade on him signing an extension with his new team; at the end of the day we don't know if he's willing to negotiate an extension or not.

From Seattle's perspective they really don't have that ready-made premier 1B/2A center you're seeking (again, depending on your definition). However, they are pretty deep in forwards, though that depth is greater on the wings than down the middle. If Toronto wants to deepen their team by turning Nylander into a couple of good but lower wattage forwards, Seattle could make a good trade partner. A hypothetical return package from them would likely include one or two Kraken forwards, with maybe some draft capital going one way or the other to balance things out depending on the players involved.