Leverkusen must definitely make transfers. Of course, they have very good players, but getting through the transfer period without buying players carries a great risk because the opposing teams now know the players' nature very well. They can resist Leverkusen better. It is rumored that Real Madrid wants to transfer Wirtz. It may be very difficult for new players to replace the players leaving the team.
I understand this condition. The Bundesliga side will learn from Atalanta who frustrated Leverkusen with possession that could not score in the European Cup final. Atalanta was able to win 3-0. Atalanta was able to make Leverkusen's strategy not go well. I'm sure at that time Atalanta had learned how Leverkusen worked with a pattern that worked very well in the Bundesliga. If the Leverkusen players are added, it will worsen Leverkusen's situation. In fact, they will find it difficult to defend the champion next season.