Diego Costa gave Chelsea a 1-0 victory over 10-man Arsenal on Sunday, damaging its London rival's bid to dethrone them as Premier League champions.
Chelsea already looked the livelier team when it gained a man advantage in the 18th minute, following Per Mertesacker's red card-lunge on Costa.
It took only five minutes after that for Arsenal's defense to be breached when Costa evaded defender Gabriel, who had been brought on to replace forward Olivier Giroud after Mertesacker's dismissal - a negative move by manager Arsene Wenger which sparked booing.
Arsenal's first home league loss since the opening day of the season leaves Leicester as the leader by three points.
The victory extended Guus Hiddink's unbeaten start as Chelsea manager to eight games, but the team only moved up to 13th.
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