An Antonio Valencia error gifted Danny Welbeck a second half goal that saw Arsenal defeat Manchester United by two goals to one at Old Trafford. Nacho Monreal opened the scoring in the first-half only to see Wayne Rooney quickly level. Welbeck put the Gunners back ahead on the hour mark, before Angel Di Maria was sent off for the hosts.

Marouane Fellaini was the man causing problems as the game kicked off, with his power and height in an advanced role causing the Arsenal defence problems. Chris Smalling fed him through with a poked ball, however his attempts to set up a chance for his teammates were thwarted by Laurent Koscielny. He did create an opening minutes later though, controlling a long Angel Di Maria ball before teeing up Ashley Young. The winger arrived quickly from the left, but could only shoot over.

It was the visitors, however, who took a surprise lead on the 25 minute mark as Nacho Monreal slotted home to put the Gunners ahead. Mesut Ozil cut in from the left hand side and spread the play to Alex Oxlade-Chamberlain, who tiptoed around three United defenders before finding an unmarked Monreal. The left-back showed good composure to control the ball, before calmly placing it past David de Gea into the bottom left hand corner.  

The Red Devils quickly responded, letting Arsenal lead for just three minutes before they grabbed an equaliser. Much maligned summer signing Di Maria sped down the right wing, before cutting inside and executing a perfect delivery to Wayne Rooney. The England striker had no problem finishing, a strong header from six yards out leaving Wojciech Szczesny with no chance.

The goals proved to be a catalyst for the game to open up, with Danny Welbeck appealing for a penalty in Arsenal's first attack since Rooney's goal. The striker looked to run onto a through ball and felt that Marcos Rojo was tugging on his shirt, going down under contact. Referee Michael Oliver deemed there not to be enough contact, signalling play on.

It was then United who attacked, an excellent Rooney touch allowing Di Maria to get in on goal. The winger didn't want to shoot on his right foot though, attempting to cut inside onto his favoured left and being tackled. It almost didn't matter, as he found himself in a similar position just minutes later. He failed to score again though, as Szczesny made a solid save to see the sides enter half-time at 1-1.

Louis van Gaal was clearly not impressed with what he had seen in the first-half, making a double change to bring on Michael Carrick and Phil Jones. Arsene Wenger was then forced into a change of his own minutes into the second half, as Oxlade-Chamberlain pulled up with a hamstring issue. Aaron Ramsey replaced him, moving Mesut Ozil out to the right wing.

Chances came and went for both sides early on in the second half as Sanchez's deflected shot was held by the welcoming arms of de Gea, before Di Maria could only strike wide when put in on goal for United.

Arsenal then took the lead again on the hour mark, through Danny Welbeck, who they signed from United last summer. A long ball from Arsenal's backline looked hopeless until Antonio Valencia's underhit pass back to his 'keeper allowed Welbeck in. The hard-working striker beat de Gea to the ball, poking it around him before slotting into an empty net.

Controversy soon followed as Rojo slid into the back of Santi Cazorla recklessly, only being punished with a yellow card before Hector Bellerin was fortunate to avoid a second yellow card for a foul on Young out wide. Manchester United players quickly surrounded referee Oliver, who gave the young full-back one more chance. Arsene Wenger wasn't in the mood to risk keeping him on, replacing him with Calum Chambers.

There was a sense that the home side would still be in the mix come the end of the game, and had chances to level as Chris Smalling and Fellaini both missed good chances from crosses into the box. De Gea was then called upon at the other end, making a world class save from Santi Cazorla's volley to keep his side in the game.

United were then dealt a major blow as Di Maria recieved his marching orders for two yellow cards in quick succession. He was booked for simulation under a challenge from Aaron Ramsey, which appeared to be a correct decision, and then reacted angrily, making contact with Michael Oliver in an attempt to appeal the decision. This left the referee with no choice other than to send off the wide man, leaving United with 10 men.

United proceeded to throw the kitchen sink at Arsenal, with long balls to Fellaini not amounting to much. Rooney was given a good chance from a free-kick with around 10 minutes left on the clock, but could only hammer the ball high over the bar. Another booking for simulation followed, as Michael Oliver continued an excellent performance by correctly booking a tumbling Januzaj.

Arsenal had another chance to finish the game off in added time as Mesut Ozil layed off Sanchez on the counter attack, however de Gea sprawled down to brilliantly deny the Chilean with his finger tips. It didn't matter however, as Arsenal saw the game out to banish their Old Trafford hoodo and secure a place at Wembley in the FA Cup Semi Finals.

Arsenal will now play Bradford City or Reading for a place in the final, whilst Liverpool or Blackburn Rovers versus Aston Villa is the other semi-final draw.