I don't think that Leverkusen is actually a team that is actually challenging for the league as far as this season bundesliga title race is concerned because if they can't even hold their own against small teams like Bremen even though am not against ten Hag I feel that it will take time before ten Hag will stabilize this team and they will become more competitive again.
I think that with the way that Bayarn Munich is conceeding goals against even small teams this will hurt them when it comes to the champions League were their are much better opponents to play against
That is the wonder of Erik Ten Hag. They are not going to win the league that much is guaranteed, even Xabi didn't win last year. But they are not going to be even near the top, that part is the part that is all thanks to him.
This team would have been top four again with Xabi, same exact squad, he would have take this team and further as well. This is why I think it's true that they made a mistake getting ETH, and they should have done a better job. If they keep making these mistakes, then they are not going to have the same exact approach to this league. Now they are just back to what Leverkusen used to be, not the team in the past 2-3 years, but the team from 10+ years ago. Just a middle team, happy to stay at Bundesliga.