Arsenal 1-2 Manchester United

Wayne Rooney has now scored 11 Premier League goals against Arsenal - more than any other player

• United record first away win under Van Gaal

• Wilshere substituted after suffering ankle injury

• We are defensively naive - Wenger

• United can still do better, claims Van Gaal

Louis van Gaal clinched his first away win as Manchester United manager as a battling display saw off Arsenal and moved his side up to fourth in the Premier League.

After long spells of dominance by the Gunners, Kieran Gibbs turned Antonio Valencia's cross into his own net before Wayne Rooney sealed victory with his side's first shot on target after 85 minutes.

Olivier Giroud came off the bench after three months out injured to pull a goal back for the hosts with a fierce strike in stoppage time, but it came far too late to rescue a point.

While Van Gaal can finally celebrate a victory on the road as United boss at the seventh attempt, Arsenal's defeat leaves them with 17 points from 12 games - their lowest total for 32 years - and a title bid in ruins.

They are already 15 points adrift of leaders Chelsea and this result was hard for their fans to fathom, given how well they started and how shaky the United defence had appeared.

Former United striker Danny Welbeck played a prominent role as Arsenal began at a whirlwind pace, but they could find no way past visiting keeper David De Gea.

The Spain international showed no ill effects from the finger he dislocated last week and his fine save after Jack Wilshere burst through was the first of many important stops.

With the Gunners completely dominant and his defence already ravaged by injuries, the last thing Van Gaal needed at that moment was another problem at the back - yet that was exactly what happened when Luke Shaw was forced off moments after Wilshere's miss.

That left Chris Smalling to marshal a five-man backline containing two rookies in Tyler Blackett and Paddy McNair and two wingers in Valencia and Ashley Young.

Initially, United's latest effort to construct a makeshift defence struggled, and De Gea had to rescue his side again after Alex Oxlade-Chamberlain escaped Smalling.

But, after a clash between Wilshere and Marouane Fellaini - the Arsenal midfielder arguably fortunate not to be sent off for thrusting his head at the Belgian - United began to find their footing.

Fellaini and his central midfield partner Michael Carrick established a foundation in midfield that allowed their side to threaten firstly through Angel Di Maria and then Rooney.

Arsenal were still creating the best chances, however, and that pattern continued after the break until they suffered two setbacks in quick succession.

Firstly Wilshere was forced off after a heavy challenge by McNair, then United took the lead in bizarre circumstances.

Wojciech Szczesny collided with Gibbs as he came out to clear a Young cross and, when Valencia fired the ball back into the danger zone, it span off Gibbs and into the net.

Szczesny could not continue, but Arsenal were missing Wilshere far more as they tried in vain to force an equaliser.

De Gea made a series of good stops but was not called upon to make a truly outstanding save and Arsenal's desperation to find an equaliser meant they left themselves increasingly open at the back.

Rooney ran clear to add a second goal and Di Maria should have scored a third when he raced unchallenged from inside his own, only to chip wide.

In other circumstances, Giroud's sparkling strike in reply would have been one to savour, but instead it offered little consolation on a depressing night for the home fans.

Olivier Giroud marked his first appearance since August with Arsenal's consolation goal

Jack Wilshere has made 21 appearances for Arsenal and England this season but limped off injured at the Emirates.

Luke Shaw, left, lasted just 16 minutes before going off injured

Alexis Sanchez has scored 12 goals in his last 15 matches for Arsenal but could not find a way past David De Gea

Goalkeeper David De Gea was in the Manchester United team despite injuring a finger while on duty for Spain