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Ten-man Arsenal missed out on the chance of reclaiming top spot in the Barclays Premier League as they went down 1-0 to Chelsea in a dour encounter at the Emirates Stadium.
The game turned on Per Mertesacker's 18th minute dismissal for a foul on Diego Costa, with the controversial Spaniard scoring the only goal of the game five minutes later to stretch the Blues unbeaten league record against the Gunners to nine games.
The result keeps Arsenal in third place, three points behind leaders Leicester and with an inferior goal difference to second-placed Manchester City, while Chelsea are now eight points clear of the relegation zone.
The visitors enjoyed the better of a cagey opening, although Joel Campbell will feel he should have made more of Theo Walcott's cross which he completely mis-kicked which allowed Chelsea goalkeeper Thibaut Courtois to collect easily.
The key moment came on 18 minutes as Costa was clean through on goal after latching onto Willian's through ball. Mertesacker interceded with a badly-timed challenge which left referee Mark Clattenburg with no option but to send the German international off.
Gunners manager Arsene Wenger responded by withdrawing striker Olivier Giroud in favour of Gabriel whcih drew widespread criticism from the Arsenal faithful inside the stadium.
Things got even worse for the home side five minutes later as Costa put Chelsea ahead after reacting quicklty at the near post to convert Branislav Ivanovic's cross.
Costa came close on two occasions to doubling the advantage and Ivanovic had an effort headed off the line, before Mathieu Flamini spurned a glorious chance to level the scores on the stroke of half time.
The Frenchman latched onto Aaron Ramsey's dangerous ball over the top, but somehow managed to put the ball over the bar when it appeared easier to score.
Chelsea shut up shop after the break, allowing Arsenal plenty of possession but very little space in the final third.
The ten men, to their credit, pushed hard for a leveller but even the introduction of Alexis Sanchez just before the hour following a ten-match lay-off couldn't prise open the Blues defence.
They lost Costa to a suspected hamstring injury midway through the second period but had little trouble holding on for a a deserved victory which puts a severe dent in Arsenal's title ambitions.