Bruno Fernandes has scored his first Manchester United goal in front of the home fans as Watford went down at Old Trafford.
Ole Gunnar Solskjaer's men secured a revenge win with a 3-0 defeat of The Hornets after they lost 2-0 in the first leg.
Fernandes opened the show with a classic PK in the 42nd minute to give United the first-half lead and later went on to add two assists.
Anthony Martial was also on target for United to double the lead in the second half with a beautiful finish, making it three goals in three matches.
Youngstar, Greenwood, completed the goals for United with a sublime finish following an assist by Fernandes.
United move from seventh to fifth on the table, three points behind fourth-placed Chelsea, as they chase Champion's League qualification.