Either the lineman got excited early and raised his flag too soon before the ball was touched, at full speed and only seeing it once he made a mistake or he felt that the player in the "traditionally" offside position was
The above is what I thought and I would have expected a United goal like that to be offside. But I'm wrong.
I think the linesman thought it was the player at the back who scored. Referee should have double checked with him.
It takes 2 mins for officials to communicate, if that. Heck, a camera replay can be done in about 30 seconds.
He's not a LB at all. I know he's done well as a CB and Mou probably wants to play him, but even Young would be better as a LB in a game of this importance. Rojo is manageable at LB in a less important game, but not a cup game.
Dunno what the fuck is going on with Shaw. He needs to get his head out of his ass and start showing he's deserving in training.