Jose Mourinho is a "miracle" for his achievements in management, according to West Ham counterpart Slaven Bilic.
But Bilic insists Mourinho remains "one of the greatest", noting the former Porto, Chelsea, Inter and Real Madrid manager's record of losing just 10 of 263 home games throughout his managerial career.
"Jose Mourinho is one of the greatest," Bilic told reporters.
"Statistically at home, there is probably no one better. But it's hard to stay at that standard and maybe that has dropped now. But only if you are comparing with his percentage from before.
"But it's impossible to maintain that for such a long period. It was a miracle that he maintained that for ten years."
West Ham sit one point above the relegation zone following last Saturday's 3-2 defeat at Tottenham, while United come into the game off the back of a comfortable 4-0 win over Feyenoord in the Europa League