The England striker’s second-half strike was enough to send the FA Cup holders through to the last four, as the Red Devils winger was sent off for diving and pushing the referee
Arsenal’s Danny Welbeck scored the winning goal against former club Manchester United on his return to Old Trafford to send the Gunners through to the FA Cup semi-finals.
Welbeck intercepted Antonio Valencia’s underhit backpass and rounded David de Gea just after the hour mark to give the Gunners a lead that they did not relinquish.
Nacho Monreal had given the visitors a first-half lead but United hit back almost instantly, Wayne Rooney nodding in an Angel Di Maria cross.
Di Maria was later sent off after receiving two yellow cards in as many minutes, the first for diving and the second for pushing referee Michael Oliver in the back, to compound another disappointing night for Louis Van Gaal’s men.
Welbeck was chosen ahead of Olivier Giroud in the Arsenal XI, while Luke Shaw came into the home side’s defence with Marcos Rojo shifting into the centre to cover for the absent Jonny Evans, suspended for six matches for spitting at Newcastle United striker Papiss Cisse last week.
Arsenal started brightly with Alexis Sanchez probing, but United were the ones who looked most likely to break the deadlock – Marouane Fellaini’s hesitance in the penalty area ending one promising situation after 14 minutes.
Arsenal withstood that pressure, though, and eventually went ahead in the 25th minute, an unmarked Monreal slotting home from close range following some neat footwork by Alex Oxlade-Chamberlain on the edge of the box.
But that lead lasted just four minutes, as Rooney got his head to a delightful Di Maria cross from the right for his 14th career goal against Arsenal.
Welbeck had appeals for a penalty turned down when he felt he was held back by Rojo as he ran into the box, while Wojciech Szczesny had to be alert to keep out a low Di Maria strike at the other end.
Van Gaal saw the need to make two half-time changes, bringing Michael Carrick and Phil Jones on for Ander Herrera and Shaw, before injury forced Oxlade-Chamberlain off to be replaced by Aaron Ramsey, the England international pulling up after challenging Rojo for the ball.
Lacking the rhythm of the opening 45 minutes, goalscoring opportunities were at a premium at the beginning of the second half, with Di Maria dragging an effort wide on the hour.
However, a Valencia slip-up at the other end cost United dear, as Welbeck pounced to punish the Ecuadorian full-back with a composed finish.
There was no time for sentiment, though, as the striker celebrated a goal against his boyhood club with passion.
Hector Bellerin could count himself lucky to stay on the pitch when he risked earning a second yellow card with a clumsy challenge on Ashley Young, and Arsene Wenger soon took evasive action by replacing the full-back with Calum Chambers.
Chris Smalling lifted over from close range with United’s best chance to pull level, and the home side’s frustrations were clear when Welbeck left the field to heckles from some sections of the ground.
De Gea got down brilliantly to keep out Santi Cazorla soon after, but United’s chances looked over when Di Maria was dismissed in bizarre circumstances.
Booked for diving, the Argentine pushed referee Oliver to earn a second yellow and his marching orders.
Substitute Adnan Januzaj then went down in the box under the challenge of Monreal with three minutes left on the clock, but he was rightly booked for simulation as Arsenal held on for the win.