North Londoners record crucial top-flight win on the road.
Arsenal overcame London rivals Fulham 1-0 away from home on Saturday afternoon, a vital victory that temporarily moved the Gunners up to third place in the Premier League table.
Arsenal, who started with England midfielder Jack Wilshere on the bench, were given a huge advantage in the 12th minute at Craven Cottage when Steve Sidwell was shown a straight red card for catching Mikel Arteta on the ankle with his studs.
Sidwell had only just returned from a three-match ban following a red card at home to QPR and Arsenal quickly asserted their advantage, with Olivier Giroud grazing the post in the 35th minute.
The breakthrough arrived from an unfamiliar source two minutes before half-time.
Theo Walcott’s free-kick was headed across goal by Laurent Koscielny and the Frenchman’s centre-back partner Per Mertesacker arrived unmarked to head the ball home from close range.
It should have been a straightforward victory, but the visitors were unable to kill the game off and then lost Giroud to a late red card after he clumsily fouled Stanislav Manolev.
Victory lifted Arsenal above Chelsea, but both the Stamford Bridge club and fifth-place Tottenham Hotspur now have two games in hand on Arsene Wenger’s side.
Chelsea will regain third place if they win at Liverpool on Sunday, while Spurs can close to within two points of their north London rivals if they overcome second-place Manchester City.