It's so hard for Rashford to challenge Raphinha for LW position. it sounds too good to be true, but let him put all of his efforts to make it happen. I believe Flick will give him some minutes to know how good he is. He can still alternatively play as a striker, and that's obvious become Lewandowski's backup as well.
I only wonder what kind of mechanism Barcelona's agreement with MU regarding his salary. It seems to me Barcelona shares his salary with MU 50:50. It's same like what Aston Villa did last season.
My thought is that Rashford would be used more as a backup striker for Lewandowski than a winger cause I see no reason why Flick would bench Rashford for Raphinha that's at his prime and doing very well in the team. Well I don't know if Manchester United would accept a loan deal since they need to sell so they'll buy their remaining target but in a case where a loan deal is accepted then both club would share the wage on a 50:50 scale.
It will be a really tough contest for Rashford to compete with Raphinha next season. Rashford is very likely to lose in this battle if we are being realistic about this. I know he impressed for Aston Villa but against Raphinha it will be a different challenge. I hope he is able to do well at Barcelona though.