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.
If Atalanta is able to beat Bayer Leverkusen, then playing in the Champion League which basically Bayer Leverkusen will playing against teams with better quality, then of course Bayer Leverkusen still has to bring in new players. At least, to prepare the team to be even better next season with the best possible rotation that can be done if Bayer Leverkusen brings in some new players. Although indeed, I also still recognize that Xabi Alonso will still be able to provide good results for Bayer Leverkusen next season but it seems, only limited to the domestic league. Because anyway, if they want to get good results also in the Champion League, then total rotation will be something that must be done, so they need second-tier players who also have good quality.