For me that has a lot to do with the way you expect United to play.
Until now I know matches against Mourinho from Bayern or Barcelona in this way - Inter-Bayern was park the bus, Real- Jupp's Bayern was an open play, Chelsea-Bayern was park the bus, Real-Barcelona park the bus.
What does he do tomorrow?
I am not so sure he will park the bus as he lacks the fast strike force and City is not so stable in their ball possession system right now as Bayern and Barcelona were. But I think Mou will plan on getting some freekicks as with Fellaini (if available), Ibra and Smalling that is a weapon
Working against a parked bus with a false nine or something similar is very difficult. That is matches in which I would prefer at Bayern to play with Lewy and Müller in the box because you have two strikerlike players who really know each other and are home in the box and it often is something they trigger that then makes you score. That are often matches in which not excellence in football but smartness let's you win.
How do you think Mourinho plans his tactics? I haven't seen a match of them now - only know that they had problems scoring and that the combined lack of mobility of a combined Rooney and Ibra might be a problem...
For me they will look to get the ball in the box via crosses asap, and that included rooney going deep and looking for Ibrahimovich or fellaini in the box or firing it out wide to a shaw or Valencia.
That is the only game plan I have seen from seeing their highlights on motd. There is not a chance on earth that Ibrahimovich will track back or run for the cause, because we will be looking for possession and control of the game.
You mention we don't have the ball retention of Bayern and Barca....which is correct but mourinho will go defence first, out of the 2 clubs it is them that cannot afford to lose this game, not us. I think you are doing Nolito a disservice with your false 9 comment, Nolito is a very smart footballer, not the fastest but intelligent and awareness of what position to take or pass to pick.
Watch the first 20 minutes very closely because united will want a fast start and will pump that ball into the box at the first opportunity, if they do score then they will close ranks. If they don't then imo we will grab firm control of the game and take the win. Their defence is the same as last season, they will be better set up but you can't replace movement and awareness via a manager talking to you.
Put our attack against their defence, and we win all day long we have the players to unlock them both ways, Silva with his passing, KDB with his crossing ability and passing, sterling with his movement and pace.
