England striker Welbeck joined Arsenal from United in a £16m deal on deadline day in September - and came back to score 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 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.

And on a great night for manager Arsene Wenger after United had won 11 of the last 15 meetings between the sides in all competitions, Arsenal are now huge favourites to reach another FA Cup final after drawing either Reading or Bradford City in the semi-final.

The hero of the night, however, was Welbeck as he punished United, the club where he scored 29 goals in 142 appearances before switching to Arsenal after Van Gaal brought in Radamel Falcao.

Falcao 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 this season and now 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 Michael 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.

(BBC)