Even when Xabi Alonso was with Bayer Leverkusen last season, their performance declined to the extent that if Bayern Munich dropped points, Bayer Leverkusen would not win their match even though they were playing against a weak team, which is one of the things that made Bayern Munich win the German Bundesliga title last season. Next season Bayer Leverkusen's performance will decline more because they will be without their best players, and they have a new coach, whom people doubt will succeed at Bayer Leverkusen.
Xabi Alonso did well in Bayern Leverkusen the first season he came in since he was able to manage the team for two seasons, and they won the Bundesliga title once. I think that is enough to say Xabi Alonso was not bad in managing Bayer Leverkusen. Furthermore, last season they were not that bad since they finished the season in the top two.
I feel like they did well, but they just did not win the title. As for this season, I can’t even argue that Bayer Leverkusen will experience a serious decline in performance because they sold their two key players and also changed their coach, and this will make everything new for this club, and they won’t be able to do well in their matches.