Well, it's 8 skaters, I don't think there's a limit on either position. In theory a team could protect 8 forwards I think or 8 defenseman, or any combination that totals 8.
The big reason why I'd protect Mayfield is because of the contract. I'd want to force Seattle to take someone with a larger contract, no matter who they are. It's an easier way to get rid of salary if we need to. Pulock, Pelech, Toews, Mayfield, Barzal, Beauvillier, Nelson, Pageau, and let them pick from what's left. If they take someone like Bailey, Eberle, or Lee, it might sting, but it moves a bunch of money out and that can be useful. We'll see what kind of deals are struck prior to then though because we already have to make some moves. Maybe whatever moves are made will help address the expansion draft too.