They need to find a way to do this, because if Marcus Rashford is signed, there's a need for him. If you're signing a player you can't play, there's a problem. Barcelona needs to get rid of players with excessive wages. This suggests they'll be selling some players during this year's transfer window. They could use the freed-up salary cap on Marcus Rashford.
Rashford really wanted Barcelona, he agree to pay cut and as well which means he also wanted Barcelona in the first place, what's now the problem is the reason why Barcelona signed him the first place. They will not bench Lewandowski, no doubt about that. They will not bench Yamal, there is no bargain about this, the only person I'm skeptical is Raphina but there isn't even a reason to have Raphina bench, that guy is too good to be replace by Rashford.
Barcelona wouldn't have given Manchester United some millions only to sign Rashford and have him entertained the fans, he is definitely going to have a play time but it will not be a full time. Raphina will play his time as usual but there are other times substitute are needed like when Lewandowski went to injury, that's what I think Rashford is here to occupied. Maybe have some time when there is emergency, Lewandowski was completely out for some months and that affected Barcelona.