It should be a must for Leverkusen to keep its players who have contributed a lot, because i think what Leverkusen needed is to maintain its players, better avoiding the clubs that targetting Leverkusen Players. So if it was happened, i think Bayer Leverkusen will be a solid team for the next season, and i believe that not only me who agree with this, but other people will agree and want to see Leverkusen matches for the next season, especially for the UCL.
Leverkusen are top club because they've set one of the longest unbeaten run in European football tournaments this season. Xabi Alonso and his entire squad was able to achieve this record based on discipline, consistency, determination and hardwork. Every member that participated inother to see that Bayer Leverkusen won the Bundesliga trophy deserves accolades. Bayer Leverkusen lost one of the important matches and it was the Europa League match against Atalanta.
Maintaining the squad is indeed one way to be able to maintain their consistency for next season, because if they continue to change players then it is difficult for them to maintain their consistency. Because basically Bayer Leverkusen is not an elite team, so with finances that are not as good as Real Madrid, it is at least difficult for Bayer Leverkusen to maintain many of its key players. But indeed, considering the way Real Madrid always has young players who are willing to stay in the team for a long time,then Real Madrid also manages to have a good performance every season, because the team has a good chemistry. Therefore, if Bayer Leverkusen is able and successful in retaining its key players then ofcourse, Bayer Leverkusen has a chance to still be able to play well in the next season.