I don't get the negativity about the first half - as so often, I feel like having watched a different game.
His task was quite clearly to collect the ball deep and bring it into the final third. He did that well (bar a few imprecise passes), playing almost 60 passes in that half alone. He was vital for United's fluidity and tried some stuff on top, which didn't really come off.
My main criticism would be that he was too passive tracking back, he could have obstructed Townsend for his goal shot, for example. He was more alert afterwards, but still.