It won't be easy for Ten Hag because several players have left the team which will certainly impact Leverkusen's performance next season, Ten Hag's failure at Man United will certainly always be remembered and that is what causes many doubts now for Ten Hag, I am the same, I doubt that Ten Hag can continue Xabi Alonso's work.
There's no also guarantee for the available players of Leverkusen can fit Ten Hag's strategy well. So, this obvious he must be building back Leverkusen in the way he wanted. Only hope Leverkusen to provide his whitelisting players such as Antony. Still hope to see goat to join them.
The only thing that you must remember is that the different coach, different approach. This is obvious Ten Hag won't be working in the same frame work as Alonso did.