#2 United would have to stretch Arsenal’s back line
Arsenal put up a dour defensive performance against Tottenham last weekend, and would want to repeat that act against United. Each of their 4 defenders, who started against Tottenham, can play actually as central defenders. It made their intentions pretty clear, and they would try to stop United’s attacks by crowding their own penalty box.
Sokratis and Laurent Koscielny were very good against Tottenham, and made a lot of interceptions and blocks inside their penalty box. United would have to stretch Arsenal’s backline to create spaces around the penalty box, and thereby penetrate into it. They can do so with probing runs through the flanks by the likes of Ashley Young, Dalot and Luke Shaw.
Romelu Lukaku is in red-hot form for United, and has scored 6 goals in the last 3 matches for them. He would again try to force his way through the Arsenal defence, and score a vital goal or two. Marcus Rashford, on the other hand, would keep making those runs to the flanks, and thereby take his markers along with himself.