The rivelry between Manchester United and Chelsea is too much that even if one side is on a multiple games losing streak, once they meet, that side on losing streak will pick form. The only advantage that Chelsea will get in this match is that Manchester United is having a final cup coming up very quick, this might make Amorim to rest his players. But if he doesn't rest players, Chelsea can't win Manchester United. I will only place my bet on this match, after the match day squad has been released. But due to the rivelry between this two teams, Chelsea should not expect any favour from Manchester United as Liverpool did them two weeks ago.
I agree with you that this two clubs don't walk on same path as their rivalry has been a long standing one, but saying that Manchester United wouldn't favour Chelsea is this game is tantamount to underrating Chelsea as though they don't stand any chance in getting all 3 points in this match. I hope if Chelsea gets to win this match the excuse from Manchester United fans wouldn't be that it's because they have a europa finals to play that's why they had to not put in so much effort in the game against Chelsea.