Next season will not be easy for Leverkusen if they don't give Xabi the new players he wants, we know they will be competing in the Champions League next season and there will be many teams they will meet with fanatical squads, in this case I hope Leverkusen management spends money to convince several players to strengthen Leverkusen next season.
Why did you say so? Is there a justification to your statements? Because I remember they have an incredible run so far in the history of European football and I'm not sure is there is any news about any player eager to live. The majority of Leverkusen players want to stay because of what they have achieve this season and who doesn't want to be associated with a good preforming club and a good coach that everyone is looking forward to have on their side.
Of course, with their success this season we cannot be sure what next season will be like, of course the Bundesliga clubs will also strengthen their sectors so they can compete with Leverkusen and other teams, next season will of course be different from this season.
No one definitely know what will happen to a team performance the next season but do you see what is happening in Premier League? For 4 seasons, a single team won the Premier League in one of the toughest league ever and they don't even looks like they are stopping next season as they are even more stronger than ever and you think another team can't do the same in another league, nothing is impossible most especially when the team and coach are too good.