The season is yet to start, but I have started to doubt Bayer Leverkusen because of what you just said. Ten Hag needs to make many things possible for Bayer Leverkusen because right now Xabi has Bayer Leverkusen reaching some level, and now for Ten Hag to manage this team, things will definitely be difficult for them because they have already left their two key players to Liverpool, and they have left their manager to Real Madrid again, which means everything will be new in Bayer Leverkusen from the coming season, and things may get difficult, especially in Champions League competition.
Ten Hag's bad luck is that he comes in to solve things when the team is in a certain decline , so the decisions he has made in the past have not been the most efficient, however now with Leverkusen he has to make a great plan, see who he can count on and what he really needs and work first with what he has, this will undoubtedly be what gives him the drive and confidence, I just hope that things go well for him, he is a Person who should have improved and corrected his mistakes.