Match ends, Manchester United 1, Arsenal 2.
- Man Utd's last realistic chance of silverware ends
- Di Maria sent off for dive and grab at referee
- Welbeck scores winner against former club
- Arsenal 11-time FA Cup winners
Danny Welbeck returned to Manchester United as Arsenal's match-winner as the FA Cup holders secured a place in this year's semi-finals at Wembley.
England striker Welbeck, who joined Arsenal from United in a £16m deal on deadline day in September, scored the goal that gave the Gunners their first win at Old Trafford since 2006.
It ensures Louis van Gaal, the manager who sanctioned his sale, will almost certainly end his first season at Old Trafford empty-handed.
Nacho Monreal gave Arsenal a first-half lead but Wayne Rooney equalised with a flying header from Angel Di Maria's cross - the high point of the Argentine's night as he was later dismissed for two yellow cards after Welbeck had restored Arsenal's advantage.
Di Maria was first booked for diving, then tugged at referee Michael Oliver's shirt as he walked away, with inevitable consequences.
On a great night for Gunners manager Arsene Wenger, Arsenal are now huge favourites to reach another FA Cup final after drawing either Reading or Bradford City in the semi-final.
United had won 11 of the past 15 meetings between the sides in all competitions.
But the hero of the night was Welbeck as he punished the club for whom he scored 29 goals in 142 appearances before switching to Arsenal after Van Gaal brought in Radamel Falcao.
The Colombian was not even called from the bench amid United's increasing panic, which saw the great tactician Van Gaal end with the giant figures of Marouane Fellaini and Chris Smalling up front.
United have sailed close to the wind on many occasions on the back of average performances this season, digging out victories without looking convincing.
There was no reprieve here, though, and now a place in the Premier League's top four and a return to the Champions League is their sole aim for the rest of the campaign.
For Arsenal, this was a demonstration of the sort of resilience that saw them win at champions Manchester City in January and ends that recent curse at Old Trafford.
And in a season when so much criticism has been aimed at referees, praise must be reserved for a magnificent performance by Oliver, who remained calm and got the big decisions right in an increasingly frantic environment.
Old Trafford has been the scene of many low-key games this season - but there was a big-match atmosphere around the stadium as United and Arsenal produced a first 45 minutes to savour.
Arsenal's crisp passing had already caused United problems before they took the lead in the 25th minute. Alex Oxlade-Chamberlain was the creator with a weaving run along the edge of the area before finding Monreal, who beat David De Gea at the near post with composure.
The lead lasted only four minutes, United replying with quality of their own as Di Maria's perfect delivery dropped between Arsenal's defenders to be met by the flying figure of Rooney, who directed a powerful header beyond Wojciech Szczesny.
Di Maria was looking much more comfortable, as well as dangerous, on the flank and he stole in behind Arsenal to get in a low effort that Szczesny blocked with his legs at the near post.
Van Gaal made a double change at the interval, sending on Phil Jones and Michael Carrick for Ander Herrera and Luke Shaw, but there was no instant cure for the uncertainty that had plagued United's defence.
And it was in evidence again as Arsenal went back in front just after the hour. Antonio Valencia's back-pass sold De Gea short and Welbeck reacted quickly to nudge the loose ball around the keeper and roll it into the unguarded net.
Welbeck received warm applause from large sections of United's support when he was replaced by Olivier Giroud. There were some jeers mixed in but he clearly remains a popular figure at Old Trafford.
Seconds after that switch De Gea produced a miraculous piece of goalkeeping to keep United in contention, somehow clawing out Santi Cazorla's shot from Alexis Sanchez's cross.
United's play, as well as the noise from their supporters, carried an air of desperation and their cause was not helped by a moment of madness from Di Maria that saw him sent off with 13 minutes left.
It was one of many lows on a night when the frustrations of United and their supporters bubbled to the surface - and their trophy hopes ended.
- 1de Gea
- 25A Valencia
- 5RojoBooked at 64minsSubstituted forJanuzajat 73'minutesBooked at 87mins
- 3ShawSubstituted forJonesat 45'minutes
- 7Di MaríaBooked at 77mins
- 21HerreraBooked at 37minsSubstituted forCarrickat 45'minutes
- 31FellainiBooked at 59mins
- 18YoungBooked at 60mins
- 2da Silva
- 39BellerinBooked at 4minsSubstituted forChambersat 66'minutes
- 15Oxlade-ChamberlainSubstituted forRamseyat 51'minutesBooked at 88mins
- 23WelbeckSubstituted forGiroudat 74'minutes
- Michael Oliver
- Shots on Target
Second Half ends, Manchester United 1, Arsenal 2.
Corner, Arsenal. Conceded by David de Gea.
Attempt saved. Alexis Sánchez (Arsenal) left footed shot from the left side of the box is saved in the bottom right corner. Assisted by Mesut Özil.
Foul by Antonio Valencia (Manchester United).
Olivier Giroud (Arsenal) wins a free kick on the left wing.
Daley Blind (Manchester United) wins a free kick in the defensive half.
Mesut Özil (Arsenal).
Aaron Ramsey (Arsenal) is shown the yellow card for a bad foul.
Ashley Young (Manchester United) wins a free kick on the left wing.
Foul by Aaron Ramsey (Arsenal).
Attempt missed. Santiago Cazorla (Arsenal) left footed shot from outside the box is close, but misses to the left. Assisted by Alexis Sánchez.
Adnan Januzaj (Manchester United) is shown the yellow card.
Adnan Januzaj (Manchester United) has gone down, but that's a dive.
Offside, Manchester United. Ashley Young tries a through ball, but Marouane Fellaini is caught offside.
Offside, Arsenal. Aaron Ramsey tries a through ball, but Olivier Giroud is caught offside.
Attempt missed. Wayne Rooney (Manchester United) right footed shot from outside the box is too high from a direct free kick.
Hand ball by Nacho Monreal (Arsenal).
Foul by Marouane Fellaini (Manchester United).
Francis Coquelin (Arsenal) wins a free kick in the defensive half.