Romelu Lukaku scored twice as Manchester United beat fellow Premier League side Huddersfield to progress to the FA Cup quarter-finals.
Lukaku opened the scoring after just three minutes, racing onto Juan Mata's through ball before finishing at the near post.
The Belgium striker then got his 21st goal of the season early in the second half as he again broke clear of the Huddersfield defence, this time picking up Alexis Sanchez's pass before calmly slotting beyond Jonas Lossl.
Juan Mata had a goal ruled out just before half time by the video assistant referee (VAR), with some confusion over whether the decision was a correct one.
But ultimately it did not matter as Manchester United maintained their hopes of winning the FA Cup for a 13th time.
Huddersfield, who are 17th in the Premier League, gave a good account of themselves and created plenty of chances in a dominant first-half performance.
Tom Ince twice went close, bending an effort just wide of the far post after being put through by Rajiv van la Parra before the former Derby forward narrowly failed to get the right connection to a Florent Hadergjonaj ball behind the defence.
However, the Yorkshire club's s focus will now return to ensuring Premier League survival.
The Video Assistant Referee is being trialled in the FA Cup and League Cup this season and opinion on its contribution has been mixed.
It was praised after correctly overturning a decision to rule out Kelechi Iheanacho's strike for Leicester in their 2-0 FA Cup win over Fleetwood last month but was also called a "shambles" by Alan Shearer for failing to award Chelsea a penalty in their FA Cup replay with Norwich.
Its contribution in this game also proved a talking point.
Mata appeared to have put Manchester United 2-0 up just before the break when he ran on to Ashley Young's neat pass but while the visiting team was celebrating, referee Kevin Friend listened to his earpiece for the VAR's input.
After a wait of around a minute, the goal was not given for offside.
Speaking on BT Sport at half-time, former United midfielder Paul Scholes said: "I don't even think a Huddersfield player was appealing for offside. It's very strange."
However, former England manager Steve McClaren, commentating on the game for BBC Radio 5 live, felt it was the correct decision to rule the goal out.
"We saw it once and our judgement was that Mata was onside. I'm satisfied after seeing it again, it's offside," he said.
"It was close. There are teething problems with VAR, but if it takes 20 minutes, that's how long it should take. If it proves that it's the right decision, then it's right to have VAR."