I put this in thr Mickinney thread, but I'll drop it here as well...
I think I see the plan developing this year. You recruit a player that profiles to play well on the outside so that you can move Leonard Moore around as required. I think that the staff loved the way Leonard Moore completely locked down Makai Lemon when they played him as the slot corner this year, and they want the flexibility to do that, again, as required... Think Malachi Toney when ND plays Miami next year.
Adding a guy like McKinney lets you decide between he and Gray as your nickel, and when the best WR on the other team plays in the slot, you can line Leonard Moore up over him and move McKinney outside into the boundary, where he gives you similar size and length to Moore.
This is really smart because it allows you to move the chess pieces around in your secondary to best defend the team you're playing against. If you're going to play man coverage, you have to have that ability.