That is the same for every coach joining a new club, they start from scratch more or less although Xabi Alonso left a good portion of an intact team behind. It's not like all the players left. Losing Frimpong and Wirtz is tough though.
When Xabi Alonso is the colour white, ten Hag is the colour black. That is what I am curious about, I want to see whether someone managing a team like Alonso can be replaced by an egomaniac like ten Hag and still be successful.
Bayer Leverkusen and Manchester United are completely different places with now it's surely challenging time for Erik ten Hag because Bayer Leverkusen is currently had better situation then Manchester United, and he can bring better results as well.
Even lost of few players surely going to have impact, but now he can bring few those could be give better, and they can keep balance in this club too much negative hype about his arrival but still he is capable of giving good results as he has done at Ajax for me, he can be successful here. Xabi Alonso done amazing stuff but now it's also test case for Bayer Leverkusen because challenges are increased, and they are having hard time for staying into good place can they survive with ETH it's another big challenge like Vincent Kompany done at Bayern Munich.
It is the other way around in my opinion because Manchester United couldn't be any worse and now if Amorim reaches top 6 with them, it won't be considered a failure. Alonso hands over. team to ten Hag that won 3 out of 3 titles and reached the Europa League final in 2023/24 and became vice champion in 2024/25. Let's not forget that ten Hag is a personality who quickly has everyone against him, including the own club management and the public press. Alonso had good relations with important people within the club and outside the club. If Leverkusen played a bad game, Alonso wasn't publicly attacked as arrogant coaches usually get attacked. Unless ten Hag has great success with Leverkusen, he will be suffering from close scrutiny and comparisons with Alonso on a daily basis.