Premier League sides Southampton and Brighton & Hove Albion also booked their places in the quarter-finals of the competition, while Swansea City face a replay against Championship side Sheffield Wednesday.
Here's a look at all Saturday's results, the remaining ties and a recap of the best of the action.
Saturday's FA Cup results
Sheffield Wednesday 0-0 Swansea City
Brighton & Hove Albion 3-1 Coventry City
West Bromwich Albion 1-2 Southampton
Huddersfield Town 0-2 Manchester United
Sunday, Feb. 18
Monday, Feb. 19
Lukaku opened the scoring after just three minutes. Juan Mata put him through on goal, and he made no mistake. Opta showed his excellent record in the competition:
10 - Romelu Lukaku has scored 10 goals in his last 10 appearances in the FA Cup. Specialist. pic.twitter.com/6z4akjVW1Q— OptaJoe (@OptaJoe) February 17, 2018
Huddersfield responded well to going behind and had the better of the first half, but they could not make their dominance count. The visitors then scored again just before half-time, but Mata saw his effort disallowed by the Video Assistant Referee (VAR).
Sports journalist Duncan Castles was not impressed with the decision:
Lukaku added a second goal 10 minutes into the second half after the visitors caught Huddersfield on the break. Alexis Sanchez slid in Lukaku, and he once again finished clinically to double his side's lead.
The Mirror's John Cross praised Sanchez for his contribution:
Alexis Sanchez is a brilliant central striker. When he plays wide, he offers no protection to the full back and if it’s a flat back four then it’s even more of a problem. Sanchez is at his best through the middle.— John Cross (@johncrossmirror) February 17, 2018
The visitors then comfortably saw the game out to keep their FA Cup hopes alive, although the VAR decision will be the game's biggest talking point.
Brighton made light work of League Two side Coventry at the Amex Stadium to secure a 3-1 victory. New signing Jurgen Locadia enjoyed a debut to remember, opening the scoring after 15 minutes.
Squawka Football showed how it was first shot on target for his new side:
Jürgen Locadia has now scored on his first appearance for Brighton in any competition.— Squawka Football (@Squawka) February 17, 2018
It was his first shot on target for them. ⚽ pic.twitter.com/OstU04cMaR
Locadia had further chances to score before Connor Goldson doubled Brighton's lead on 34 minutes; the defender headed home Markus Suttner's corner for an incredibly rare goal, per Opta:
669 - Connor Goldson has scored his first competitive goal for Brighton since April 2016 versus QPR – 669 days ago. Rush.— OptaJoe (@OptaJoe) February 17, 2018
Coventry did have chances to score, but Leonardo Ulloa headed home Brighton's third in the second half to put the game out of reach.
Opta showed how long Ulloa, in his second stint at the club, had gone between goals for Brighton:
1386 - Leonardo Ulloa has scored his first goal for Brighton since May 2014 against Nottingham Forest - 1386 days ago. Return. pic.twitter.com/vf97B0Qu7r— OptaJoe (@OptaJoe) February 17, 2018
Jonson Clarke-Harris grabbed one back for Coventry, but it was just a consolation for the visitors as Brighton make the last eight in the FA Cup for the first time since 1986.
Southampton also tasted victory and poured more misery on Premier League bottom side West Bromwich Albion.
Albion's preparations for the game had been disrupted after an incident during a training trip to Barcelona. BBC Sport explained their troubles:
Things got even worse for the Baggies at the Hawthorns, as goals from Wesley Hoedt and Dusan Tadic put the visitors into a 2-0 lead. Salomon Rondon then volleyed home brilliantly to halve the deficit before Ahmed Hegazi hit the bar late on, but it was not enough for Alan Pardew's side.
TalkSport's Mike Parry summed up the current situation at the club:
It's agony upon agony for West Brom. The disgrace leading to their exit from the FA Cup has terribly damaged a really great football club. Pardew and all 4 players should be summarily dismissed for the shame they've heaped on a team with some of this country's most loyal fans— Mike Parry (@mikeparry8) February 17, 2018
The Baggies are bottom of the Premier League table by five points and also have the unwanted fallout from their trip to Barcelona to contend with.