Chelsea and Manchester united are in the same exact condition. The blues performance is purely mediocre and having these players, playing like novice.
I think Chelsea and Manchester united problems are separate issues. For Chelsea; they have a new disjointed team of promising players with little experience, and few quality players in the team; this leads to conflicting performances in the team. For Manchester United; it is more of a tactical problem than injuries; Ten Hag is getting exposed tactically; and deserves the blame; he can only deflect the pressure for a while.