Rashford joining Barcelona is going to affect some players in the squad, players like Dani Olmo and Fermin Lopez, this players play as a midfield and i believe Hansi flick will use Raphina in the midfield in some matches and Rashford to play as a winger, Rashford might not complain about the minutes he play but he will not like it when he is being benched more than 5 matches.
This makes perfect sense, as Hansi Flick will undoubtedly need rotation to maintain player fitness and will use Rashford to replace Raphina.
However, for important competitions, Hansi will undoubtedly continue to use Lewandowski as a center forward.
Rashford's arrival will undoubtedly provide Barcelona with additional performance strength, giving the club a significant opportunity to win several titles next season.