Rashford simply needs to play according to the coach's instructions when he's deployed in his preferred position, as the Barcelona coach will then assess Rashford's level of cooperation with his teammates. Barcelona is currently striving to make significant improvements in order to have a better season and free itself from financial difficulties, so Barcelona should be able to win several major competitions next season. And Rashford's arrival at Barcelona could at least add a little strength that could have a positive effect on the team as a whole.
It's not certain that Rashford will get playing time; it won't be easy, with Rapinha and Lewandowski also in the squad, so Rashford will have to compete for a starting spot.
Barcelona's reason for signing Rashford was to fill a void, similar to last season when injuries caused a dip in performance. If he wants to develop further, Rashford will have to prove himself in the limited opportunities he's been given.
Barcelona will surely face several championships this year, and it will not be easy to have the whole team that can manage all the appointments both in the league and in the European cups, therefore Rashford comes into play, he certainly will not start, but then as we know things can change quickly and from the bench he could earn a place in the starting lineup