Van Gaal looks set with the two sitting midfielders, usually two of Schweinsteiger, Carrick and Schneiderlin. I don't think Herrera is suited to the way he wants those two sitting midfielders to play, but he could be great as the #10 in this formation, as we saw in the 2nd half.
His natural instincts as a footballer seem to be that he always wants to be involved, and to be where the ball is, so as a #10, he will probably perform like a hybrid of a #8 and a #10, dropping deep, bringing the ball forward and getting into the box. He will link the sitting midfielders to the attack, which is something that has been lacking so far. There's often a huge gap between the front and the back, and nobody to fill it.
Januzaj can make things happen with the ball, but he's not the man to link it all together. Not yet anyway. Herrera and Mata are much more suited to that, and with Herrera's tenacity off the ball as well, I think he should be given a run in that position.
Rooney
Memphis ------------- Mata ---
Herrera
Carrasteiger Schneiderlin
Solid.