Back to Rashford. I re-read an article that I have read a month ago (and forgotten most of the details), and recall something interesting.
http://www.bbc.com/sport/football/36313516
He had played at right winger in youth matches (though this article never specifically telling it is at the right wing, I am rather sure that I read in other articles that, he played right winger/right forward before). So that is not something unfamiliar to him.
What's more interesting is:
He can play back to goal, the Jose kind of striker role. However, the youth team coaches must have seen something unique in him:
There is another article that I just read, today. The author is rather confident that, Rashford will have times under Jose, and be played at the No 9 role.
http://www.unitedrant.co.uk/opinion/mourinho-and-marcus-the-special-match/
We can look at this from a few aspects.
Do Jose play single striker (433, 4231, his Chelsea time) or double strikers (4132, 4312, his Inter Milan time). If it is the double strikers formation, for sure Rashford will have more time. A combination of Zlatan + Rashford looks promising.
But, if it is the single striker role, then it depends on whether Jose trust Rashford as his single striker. If he doesn't trust, we may see Rashford more on the winger/forward role. When Zlatan is rested or injured, we may see Rooney back to his striker role, or we may even see Jose bringing in another backup striker to Zlatan (recall Demba Ba, Loic Remy?) If he trusts Rashford, then, things will be interesting. I think he will change his style, setup, to accommodate Rashford instead of forcing him to play back to goal style (I know, this is contradicting to what I have said in my previous post). People are saying that, Jose does change his setups. For example, he usually does not play a deep-lying playmaker, but he played Fab at Chelsea, Alonso at RM. Ball playing CB is not the typical CB that he likes, but he wanted Stones. So, it seems that he does change.