One thing people seem to have forgotten is that he doesn't do very well under pressure. It's got something to do with his personality. There were instances in the past where he was being put under the spotlight for his and his team mates performances and he just had to talk back in order to justify his past actions. Talked instead of doing something about it. Even when he was doing well at Inter he still had to talk about United. It's like he's very conscious of his self image. I think it's why he didn't meet expectations at United, he was really good at convincing himself that things are going fine and he hasn't done anything wrong. You can't really compare his career at United vs at Inter. At Inter he didn't have a lot of pressure to begin with, they had never won the league for how many years? he joined and instantly became a favorite for Conte and it was during the time when things can't go worse after United. Sure he worked hard under Conte but that's only the physical part. It's still the same person. I think if his career at Chelsea goes smoothly in the first few months and over the course of the season, they have themselves a top goal scorer (only scoring goals though!). But if there's something wrong that happens, that reverts himself back to "I'm doing good really. Let people talk, I do the thing" etc. then it could spell a disaster. Especially if Tuchel starts to favor other strikers instead of him, if it ever goes that badly.