I don't feel Pep Guardiola need to sign a new player for the role of Kevin DeBruyne to be filled, Manchester city have alot of midfielder that can take over the role until he recovers. They have Bernardo Silva that just signed a new contract recently that can take over from where Kevin DeBruyne left and he'll do a perfect job because he has similar characteristics as Kevin DeBruyne as they're good passer of the ball but nobody can replace Kevin DeBruyne because of his quality on the ball. The Manchester city midfield also have Mateo Kovacic would is also a good midfielder and can hold possession of the ball and control the midfield with Phil foden also been in the picture so the Manchester city midfield has a lot of players to fill in the shoe of Kevin DeBruyne and now Pep Guardiola just have to trust one of them to do the job appropriately.
Manchester city and Real Madrid had something that Barcelona didn't have and that's the financial backing to sign all this top players that are making waves recently and not because Barcelona is no longer a top club. They still have a history and player would want to sign for them instead of other clubs and this came to display last season when they had transfer window war with Chelsea on some top players that both club wanted and they choose Barcelona over Chelsea on all occasions and that's to show that Barcelona still got what it takes but they're lacking the finance backing to actually chase after this players as they can't offer them the same wages as those these other two clubs will offer them and players are going where the money is this days.