London - Diego Costa scored as Chelsea renewed their hold over Arsenal with a 1-0 win at the Emirates Stadium on Sunday that dented their London rivals' Premier League title hopes.
Costa had been the central figure in Chelsea's 2-0 win over Arsenal in September, when he goaded Gabriel into getting sent off, and he drew the foul that saw Per Mertesacker dismissed in the 18th minute before neatly converting the game's only goal five minutes later.
It was Arsenal's first defeat in 10 home league games and left Arsene Wenger's side in third place, below Manchester City on goal difference and three points shy of leaders Leicester City.
Chelsea rose one place to 13th, calming any relegation concerns, after only their second win in six league games under interim manager Guus Hiddink.
Arsenal, who welcomed Alexis Sanchez back from injury, have now gone nine league games without beating Chelsea, during which they have not scored in over nine and a half hours, and their latest failure left them without a win in three league games.
Chelsea remain 14 points below the top four, but while Champions League qualification remains an unlikely goal, this was further proof that, even without the departed Jose Mourinho, they continue to hold the Indian sign over Arsenal.
Arsenal recalled Mesut Ozil after he missed the 0-0 draw at Stoke City with a sore foot and he was a typical buzzing presence as the hosts forced their opponents back early on.
But Arsenal lacked precision in the final third, Joel Campbell miscuing a volley from Theo Walcott's cross and Mathieu Flamini slipping as he attempted to shoot, and the best chances fell to Chelsea.
In the second minute, Petr Cech had to drop to his right to turn a shot from Oscar around the post after Laurent Koscielny had tamely conceded possession.
When Cesar Azpilicueta crossed from the left, Willian was given two bites at the cherry, seeing his initial volley scuffed back to him by Mertesacker and then putting his follow-up straight at Cech.
In the 18th minute came the game's decisive moment. Costa reached Willian's through-ball just ahead of Mertesacker and with the German already committed to a sliding tackle, the Chelsea striker tumbled and referee Mark Clattenburg brandished the red card.
Gabriel, sent off for kicking Costa in September, unsurprisingly came on to plug the gap, but there were boos when the number held up on the fourth official's electronic board was striker Olivier Giroud's.
It was typical of Costa to find himself centre-stage and barely a minute after Gabriel's entrance, he stole between the Brazilian and Koscielny to convert Branislav Ivanovic's cross with an adroit near-post volley.
The Spain striker threatened to add a second before half-time, but after gathering Willian's square pass with a clever touch that took him past Nacho Monreal, his shot was repelled by Cech.
From the ensuing corner, Ivanovic's header was headed off the line by Monreal.
Arsenal finally got in behind Chelsea in first-half stoppage time when Aaron Ramsey clipped a pass into the area for Flamini, but the Frenchman -- not renowned for his penalty-box prowess -- jabbed a volley over.
With Chelsea continuing to probe in the second half -- ex-Arsenal favourite Cesc Fabregas seeing a strong penalty claim waved away after being impeded by Koscielny -- Wenger turned to Sanchez.
The Chilean, sidelined for 10 matches with a hamstring injury, replaced Campbell and spurned a chance to level when he took an airshot as the ball ricocheted around the Chelsea box following a free-kick.
Costa departed, beneath a hail of boos, in the 68th minute, with Loic Remy coming on, while Eden Hazard made his return following a three-game groin injury lay-off as a replacement for Oscar.
With Wenger watching anxiously from the corner of his technical area, a late chance fell to Flamini, but his deflected back-heel was fielded by Chelsea goalkeeper Thibaut Courtois.