Watch Romelu Lukaku Score As Manchester United Defeat Derby County 2-0
A replay looked on the cards for Manchester United who left it late until Romelu Lukaku laid the ball off to Jesse Lingard, who took a touch and sent a 20-yard shot on the bounce into the top corner.
And half-time substitute Lukaku sealed the win after playing a one-two with Anthony Martial to cap off a counter attack.
United striker Marcus Rashford had hit the post in both halves – with a close-range header that he should have buried and a fierce shot across goal.
Rams keeper Scott Carson was excellent, making eight saves, including fine stops to keep out Juan Mata and Paul Pogba free-kicks.
Derby, second in the Championship, played well and Tom Lawrence forced a good diving save from Sergio Romero.