You can't compare Chelsea to Manchester United from the fact that it has been obvious especially during pre season that Chelsea defense is wack while Manchester United issues goes more than being the defense but all part of the team there haven't actually been a notably growth from them but their coach is too blinded to see, all because of his shameless pride but like they say pride comes before the fall.
Enzo Maresca's defense choice has a lot of scrutiny but I won't judge more till next season or January let's see if there will be an improvement at the Cb especially
It seems to me that the poor defensive performance of Chelsea and Manchester United may be a common problem that Maresca and ten Hag were unable to solve in the off-season, despite significant spending on new transfers. Maresca is just starting to take his first steps at Chelsea, he may be forgiven for some mistakes, but despite this, I think the decision to fire Pochettino was a big mistake. And ten Hag has no time, they decided to give him one last chance and allowed him to stay as a coach, but the start of the season for Manchester United was a failure, I can’t imagine how this can be fixed.