Jesse Marsch's side found themselves with a mountain to climb inside half an hour when Luke Ayling was shown a straight red after a quickfire brace by Eddie Nketiah gave the hosts an early, comfortable lead.
With ten men, United put on an admirable showing to chase a result after the interval but Diego Llorente's second-half goal proved only a consolation as the Whites failed to find an equaliser in North London.
The defeat allowed Everton to climb out of the relegation zone with a 2-1 victory at Leicester City, causing the Whites to drop below the dreaded dotted line, level on points with 17th-placed Burnley but with a significantly poorer goal difference than their Lancashire counterparts.
Graham Smyth, the YEP's chief football writer, hands out the scores from Sunday afternoon's clash at the Emirates.