Memphis Depay's first-half strike has put Manchester United on course to beat Watford and take top spot in the Premier League for the time being.
The Red Devils, sometimes criticised for their style of play this season, made their intentions clear early on with two menacing crosses although Watford survived.
However, the Hornets nearly fell behind in comical circumstances when Allan Nyom's attempted clearance was miscued and almost dropped into the back of Heurelho Gomes's net.
United's early attacking was rewarded when Ander Herrera's pinpoint cross was met by a crisp volley from Depay, which beat a helpless Gomes.
Watford, who would go above Liverpool with a win at Vicarage Road, were nearly caught out again when they initially failed to clear Daley Blind's ball into the box, but Quique Flores's men remained only one down.
Instead, the hosts wasted a good chance to equalise when Ashley Young gave away possession before Odion Ighalo fired harmlessly wide, when he had a number of teammates waiting for a cross.
The visitors suffered a blow when Herrera limped off the field, but continued indecisive defending from Watford provided Morgan Schneiderlin with another chance, only for the French midfielder's shot to miss the target.
After Troy Deeney made an acrobatic clearance to deny United once more, Etienne Capoue then missed the target at the other end when he found shooting space in the area.
