Signing Rashford is the best thing Flick has done to Barcelona this season they missed signing Nico Williams so getting Rashford even though its on loan is an opportunity to strengthen that wing since I heard he wants to use Raphinha as an attacking Midfielder. Rashford would add lots of strength to their depth and he's already fine in the training ground.
Rashford is definitely an asset as seeing that he has wanted a place like this away from Manchester United where he st a point was not enjoying the environment and so just to prove them wrong he will want to do better in Barcelona, I did went to see his goals and his performance in subsequent games before now and I see that he is a very brilliant player who just needed that environment that will give him the chance to be more spectacular which I am believing Barcelona will give him one.
If being away from Manchester United and it's environment will make Marcus Rashford get back to his form and become a better player then moving to Barcelona is the best then for him at the moment, in Barcelona he will meet young players and he will be motivated to work on his fitness, train harder and try to become a better player that he is. He will be facing a competition in the team he has to do better to be able to become a regular starter for the team.