Yeah, the fact that Herrera was sanctioned by van Gaal and not targeted leads me to think he's the most dispensable in his eyes.
Even if we were to bring in Strootman, I'm still not convinced that any of the midfield variations would be quite 'there'.
I don't love the sound of Rooney, Blind and Strootman.
Di Maria, Herrera and Strootman has the speed and energy, but lacks the discipline.
Di Maria, Blind and Strootman maybe lacks the energy and speed, but could work.
I think we may end up with what you predict: Rooney ahead of Blind and Strootman, and Di Maria wide.
Can't say I'd love that, but maybe it would surprise us.