I don't understand the plans of Ten Hag for Bayer Leverkusen team he has been selling out the key players that has helped the team reach the milestone it has gotten to in terms of been competitive against the dominant opponent Bayern Munich when Xavi Alonso was manning the head coach position. Despite this sells I haven't seen some an equal replacements to these players leaving the team. I am already doubting Leverkusen m's ability to do much in next season's competitions like they did under Alonso.
It's not ten Hang that is selling but the club plus the players are willing to leave so you will not blame ten Hag for the massive departure of players from Leverkusen he has to only work with the players that are available while still looking out for top quality players to bring in and strengthen the team
Perhaps not all the sells are coming directly from his decision but as a coach he should have the charisma to convince some of the players to stay even tho they wish leaving he could at least talk to them to have faith in his project for the club as new manager to avoid such departures because it's really going to affect his first season with Leverkusen.
There is nothing Ten Hag can do to stop those players from leaving, because they have already made up their minds and have a new deal. However, they might not listen to him because they don't have confidence in him.
The players knows what he did to United and might feel that the same thing will replicate itself in Leverkusen. Ten Hag can get a player of his choice which is the dream of every coach.