Thinking a little more about a Santiago in the slot once in a while scenario:
First, it's a total mismatch on a LB as far as speed if John runs a route. That moves a safety over the top for support. Brady and Oscar would love that.
Next, if you motion him across (jet sweep) that forces the CB on the side he's running toward to make a decision: either stay on top of the receiver on that side and get blocked and possibly lose contain or shift to outside leverage (in the hope of keeping Santiago inside, contained, where there's tackling help) but that gives the WR the quick inside slant, and that's a throw Studsrud can make.