Leverkusen are a very good and organized team and they performed well last season and won the German league title and this season their performance was also excellent so it will be easy for Ten Hag to manage the team if he does not overdo it. If the thing is that the previous manager changes everything and puts players of his choice in the starting eleven and manages the team with a different strategy then the performance will be bad. I think if he does that the Leverkusen fans will never accept this so he will try to manage the team within his means. If Leverkusen performs better under him then his team management will be praised but if he cannot manage the team properly and if the team does badly under him then he will be considered as a bad manager as he was before.
The team is not the same team. Frimpong and Wirtz is gone, and those two were very important pieces of the team, so now that they are gone, ETH doesn't have the same team as Xabi had. abi was given a chance to keep those players while he was there, Leverkusen knew that they couldn't keep Xabi forever, and they knew these players were young and could be sold when Xabi leaves and they did that.
Now ETH is given a "worse" team, but some money, so lets see what kind of team he will build but it's obvious that we are not going to see them be as good as they used to be. I am telling you, I have said this before, I bet that they will have hard time being in the top four, and that is a clear thing, I am sure that we are not going to see them be that good.