You probably said the same about Temo Werner or Havertz. Your players don’t do well over here and neither will he. It’s a tougher league and he doesn’t have to quality to adapt at West Ham let alone Manchester United.
I won't restart the tiresome general discussion about how bad BL players adapt to the PL and I don't think I was very active on here (or at all) when those two transfers happened, so I won't be able to prove what I am going to say now, so just take my word for it please
Timo Werner always was a player who relied a lot on his pace to strike on counter attacks. And he had just one season were it all came together for him in the Bundesliga. It was not a big surprise to me that he couldn't hit the same numbers for a Chelsea team that relied less on lightning fast counter attacks than Leipzig did. Nonetheless I think he was a decent and hard working player for Chelsea. Not as good as many hoped, probably a bit more unlucky than he should have been, since that time lost somewhere and doesn't even start for Leipzig now.
Kai Havertz is a curious case. He had many great moments and decided crucial games, yet overall he just was too inconsistent. I would have expected him to show his best form more often than he did at Chelsea.
But the most crucial part of this discussion is the level we are talking about. Just assume you sign him, he starts from now on every PL match and scores just two or three goals. You would rightfully say that this is terrible and that he failed to adapt to the PL. And still I would be right because I called him a good alternative to Højlund who scored 0 (in words: zero) PL goals so far this season.
Why is that? Is he Mbappe and has clubs like Madrid lined up to take him?
In an interview published today Stuttgart's CEO Alexander Wehrle claimed that Guirassy had financially better offers in the summer and still decided to stay in Stuttgart because he likes living there and being a crucial part of a well-functioning team (keep in mind they only became that late last season after Hoeneß took over as manager and Guirassy returned from injury). Assuming that he speaks the truth we can deduce that you would need to offer him quite a lot to join your broken team. Wehrle also claims that there currently is "no indication" that Guirassy is going to move in the winter.
https://www.bild.de/sport/fussball/...cht-ueber-guirassy-wechsel-86531752.bild.html