Harry Maguire's controversial stoppage-time header secured Manchester United a dramatic 2-1 FA Cup victory over Leicester City at Old Trafford.
The former Leicester defender nodded home Bruno Fernandes' free-kick in the third minute of added time, though replays suggested he was in an offside position.
With no VAR in operation for the fourth-round tie, the goal stood, sparing United's blushes against the struggling visitors.
The holders narrowly avoided a cup upset after producing another underwhelming display that saw them trailing at half-time.
Harry Maguire scored from what appeared to be an offside position against Leicester
Reuters
The late winner completed a hard-fought comeback for Ruben Amorim's side, who have now progressed to the fifth round of a competition they won last season.
Leicester City, who have won just two away games all season, took control of the first half as United produced a tepid display.
Bobby De Cordova-Reid put the visitors ahead three minutes before the break, capitalising on Andre Onana's weak save to score from close range.
United failed to register a single shot on target in a dismal opening 45 minutes that left the Old Trafford crowd frustrated.
Manuel Ugarte was particularly culpable for the hosts, losing possession in the build-up to Leicester's goal and struggling to make an impact in midfield.
New signing Patrick Dorgu endured a difficult debut at wing-back, lasting just 45 minutes before being substituted at half-time by Amorim.
Amorim's decision to introduce Alejandro Garnacho at the interval proved transformative for the hosts.
The Argentine winger injected much-needed energy and directness into United's attack after replacing Dorgu.
Garnacho nearly got on the scoresheet himself when he lifted the ball over the goalkeeper, only for Caleb Okoli to make a remarkable goal-line clearance that sent the ball onto the crossbar.
There is no VAR in the FA Cup until the fifth round, meaning there was no check on Harry Maguire's goal
Reuters
The substitute's impact was eventually rewarded in the 68th minute when he played a key role in Joshua Zirkzee's equaliser.
Zirkzee, who has endured a difficult spell since his £34m summer move, finished tidily to bring United level when they desperately needed someone to make a difference.
The goal marked a significant shift in momentum as the holders pushed for a winner in the closing stages.
The dramatic finale saw United awarded a free-kick in the second minute of three added on at Old Trafford.
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Joshua Zirkzee came off the bench to score the equaliser against Leicester
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Bruno Fernandes, who had been largely anonymous throughout the match, delivered a brilliant set-piece into the box.
Maguire rose highest to head home against his former club, sending the home crowd into celebrations despite Leicester's protests about his positioning.
The goal maintained United's hopes of becoming the first team since Arsenal in 2014-15 to retain the FA Cup.
It was a fitting end to another eventful night in Manchester, though questions remain about United's overall performance despite the victory.
The win sees Amorim's side advance to the fifth round, having survived one of their sternest tests in their defence of the trophy.
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