They can start SWR and Ober for Friday's games, Festa Saturday, and Lopez Sunday, if they want.
They'd have Ryan Monday in KC, but nobody for Tuesdays game.
Or, they can bring up a spot starter for Friday's doubleheader using the 27th man. I suspect they take this route. It keeps the rotation sort of intact, and makes best use of the 27th man. If they use 2 regular starters for the doubleheader they'll need someone else outside the rotation to start a game against KC anyway. Might as well do that when you have an extra roster spot that won't require roster manipulation