Manchester United should keep a player like Rashford in the team even if he is not in the starting lineup, Rashford is a good player and if he has a good coach he will have a better season, Manchester United can use Rashford as a striker, Manchester United looks broke to me because they can’t sign good players like the other clubs are doing since the transfer window.
I don't think Rashford would get any other opportunity in Manchester United, Amorim made it clear when he arrived, though i don't know why he came to such a decision, the attackers in Manchester United are not any better than Rashford. United keep hiring managers who cannot keep some of their pride aside and coach the team, that's why they keep clashing with players, Amorim is going down that same direction, just like his predecessor, Ten Hag, and we saw how that ended for him.
Barcelona are also in an intense push to sign Marcus Rashford. But now it's up to him, like now it's up to Rashford whether he wants to stay at Manchester United or wants to move to other clubs. The boss of Manchester United already expressed his opinion that he didn't need Marcus Rashford, and that's why I believe that he would move to Barcelona rather than stay at Manchester United. Barcelona-supporting director are on the way to meet his agent to discuss the deal.
Hansi Flick needs a natural winger, while Marcus Rashford is a precious natural winger, and indeed his move would be make sense because the Barcelona team is feeling the lack of a left winger.