Sam Allardyce, the West Ham manager, feels it has been "scary" to see Manchester United's dominance of the Premier League this season.
United could stretch their lead at the top of the table to 18 points with victory at Upton Park, which would leave them within touching distance of the title once again.
Allardyce believes the way Sir Alex Ferguson's side have gone about wrestling back superiority from rivals Manchester City, spearheaded by the goals of £24m signing Robin van Persie, has been awe-inspiring.
"You have to say the [United] team is as good as it has ever been because nobody normally wins the title so easily and by so big a margin, or has this much of a margin at this stage of the season," said Allardyce.
"It is pretty scary what total they might finish with. Manchester United have been outstanding. Their squad rotation has been Sir Alex's masterpiece as usual, about playing the right team at the right time.
"You could say that because they got knocked out of the Champions League a little sooner than usual and because they got knocked out of the FA Cup and Capital One Cup, it has given them the strength and energy to be what they are in the Premier League this year.
"They have not had the normal focus on three or four competitions almost to the end, the focus has come on the Premier League and they have just breezed it. Everyone else can't get near them."
West Ham have pushed United in their meetings this season – coming within moments of knocking them out of the FA Cup third round at home in January before Van Persie equalised deep into stoppage time.
"We will need to be on our best form, as always, if we are to get anything," said Allardyce, who has defensive problems with James Tomkins struggling with a calf injury and facing a fitness test.
Odds West Ham 9-2 Draw 11-4 Man United 4-6
Referee L Probert (South Gloucs) TV Sky Sports 2