Arsenal 0 Chelsea 1: Costa nets winner after Mertesacker dismissal
Chelsea extended their recent good run against Arsenal, who had Per Mertesacker sent off in a 1-0 Premier League defeat at Emirates Stadium.
Diego Costa proved to be the scourge of 10-man Arsenal once again by playing a pivotal role in Chelsea's 1-0 Premier League victory at Emirates Stadium on Sunday.
The Spain striker was embroiled in a spat which saw Arsenal's Gabriel sent off in the champions' 2-0 win in September, while also clashing with Laurent Koscielny in that game.
The latter of those confrontations earned him a retrospective three-match ban, but Costa had an even more decisive impact here.
In a five-minute period midway through the first half, Costa drew a professional foul from Per Mertesacker that saw the Arsenal defender sent off, before netting the winning goal from Branislav Ivanovic's excellent delivery.
Even the second-half introduction of Alexis Sanchez - featuring for the first time since suffering a hamstring injury in November - could not spark Arsenal, who lost at home in the league for the first time since the opening weekend of the season.
Victory means Chelsea remain unbeaten since Guus Hiddink replaced Jose Mourinho and they have not lost in their last nine league meetings with Arsenal, who are third, three points behind leaders Leicester City.
Both sides had sights of goal in the opening two minutes as Joel Campbell missed his kick from Theo Walcott's cross before Oscar - recalled in place of Pedro - had a shot tipped behind at the near post by Petr Cech.
The former Chelsea goalkeeper was called into action again in the 15th minute as Willian fired straight at him after Arsenal struggled to clear.
And Willian was heavily involved in the sending-off three minutes later as his throughball released Costa, who looked to break away only to be brought down by Mertesacker, leaving referee Mark Clattenburg little option but to brandish the red card.
That dismissal prompted Arsene Wenger to send on Gabriel in place of Olivier Giroud, but Arsenal were almost immediately behind as Ivanovic's superb cross from the right was turned in by Costa from close range at the near post in the 23rd minute.
Costa went close to doubling his tally shortly before half-time only for Cech to save sharply, and from the resulting corner Ivanovic's header was cleared off the line by Nacho Monreal.
For all Chelsea's superiority, Arsenal had a chance to level with the final act of the first half but Mathieu Flamini volleyed Aaron Ramsey's clever pass over the crossbar.
In a quieter second half, Chelsea felt they should have had a penalty shortly before the hour when Koscielny body-checked former Arsenal skipper Cesc Fabregas, but Clattenburg was unmoved.
A frantic scramble in the Chelsea box raised Arsenal hopes of an equaliser, but the hosts could not force the ball in as Hiddink's side stood firm to claim back-to-back away wins and move above West Brom into 13th place.
Key Opta stats:
-Arsenal have now gone nine hours and 32 minutes without a Premier League goal against Chelsea.
-The Gunners' six games without a goal against Chelsea has equalled their Premier League record for the longest scoreless run against a single club (also six against Liverpool between 1997 and 2000).
-Chelsea are unbeaten in their last nine Premier League meetings with Arsenal (W6 D3).
-Diego Costa has scored six goals in six games under Guus Hiddink (all competitions).
-Chelsea have won back-to-back Premier League away games for the first time this season.
-The Blues are on the current longest unbeaten run in the Premier League (W3 D4).
-Arsenal have been shown more red cards against Chelsea than they have any other Premier League opponent (7).
-The Gunners have failed to score in consecutive league games for the first time since August 2012.
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