This is why we shouldn't underestimate Ten Hag. Leverkusen wouldn't expect too much from Ten Hag because they have known his past and hiring him means that they're ready to work with him. On the other hand, Ten Hag will also want to put in the best of his coaching skills into the job, so that Leverkusen wouldn't be disappointed in him.
A more tangible change will be seen when the team and coach truly collaborate. When the coach, team, and players are in sync with the coach's strategy, the team will certainly achieve more tangible results. I'll also be watching Leverkusen's performance next season, and I'd be delighted if Leverkusen can make a bigger difference in the Bundesliga next season. Leverkusen needs to be superior to both Bayern Munich and Dortmund next season in the Bundesliga.