N. Monreal, W. Rooney and D. Welbeck scored. A. Di Maria sent off

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.