Someone has to go next year, and the Knights already have 1 too many defensemen.
McNabb is a UFA so he's the obvious choice to let go, but maybe the Knights choose to re-sign him and deal Hague instead.
If Hague wants top 4 D money to play 3rd line LD minutes and McNabb is willing to take a discount to finish his career in Vegas, could see a trade happening.
If the Knights were to deal Hague they'd probably want a good young forward in return.