Harry Maguire was sent off as beleaguered Manchester United manager Ole Gunnar Solskjaer suffered more misery in an emphatic defeat at Watford.
The Hornets should have gone ahead when Scott McTominay bundled over forward Joshua King inside the box, but goalkeeper David de Gea saved Ismaila Sarr's penalty - then kept out his retake, ordered by the referee for encroachment.
Kiko Femenia had actually converted the rebound from Sarr's first spot-kick - but he had encroached too, so the goal was ruled out as the retake decision was made.
King opened the scoring thanks to Emmanuel Dennis' assist, before Sarr atoned for his penalty failures by sending a right-footed shot across De Gea to make it 2-0.