Premier League leaders Chelsea left Arsenal's title challenge reeling by beating the Gunners to increase the gap to 11 points on their London rivals.Striker Didier Drogba guided an Ashley Cole cross into the top corner to put the visitors ahead.Another Ashley Cole delivery was then diverted into his own net by Arsenal defender Thomas Vermaelen.Drogba put an elaborate seal on a deserved victory when he powered in a 25-yard free-kick late on.Arsenal boss Arsene Wenger had said the game was a moment for his players to show their strength but, instead, the defeat only served to blow a massive hole in his side's title hopes.Chelsea, however, move five points clear of Manchester United at the top of the table and have now kept clean sheets in their previous six Premier League matches.The last time Arsenal had been beaten at home was by Chelsea in May and, despite five wins from as many league games at the Emirates Stadium so far this season, the Blues again showed their power was superior to Arsenal's panache.Wenger's side had quickly got into their passing stride but struggled to pierce the visitors' backline and Chelsea could have had an early penalty in their favour.Striker Nicolas Anelka had a shot blocked by keeper Manuel Almunia when through on goal but, in the process, seemed to have been pulled down by Bacary Sagna.There was little protest from Chelsea and they worked another opportunity which saw Drogba fail to get enough power on a header he angled straight at Almunia.For all their possession, Arsenal had little to show for it and they were handed the harsh lesson in the necessity of having a ruthless streak to their play.Former Gunners left-back Ashley Cole responded to the boos greeting his every touch by curling in a cross which Drogba finished with aplomb for his ninth goal in his last nine appearances against Arsenal.Soon after, a whipped Ashley Cole cross to the near post was diverted into his own net by Vermaelen as Arsenal were left stunned on the stroke of half-time.This was the cue for Wenger to introduce Theo Walcott at the break in an attempt to get behind the formidable Blues back line.His introduction gave Arsenal fresh impetus and the hosts thought they had pulled a goal back when Andrey Arshavin drove in a shot at the far post. But the goal was disallowed for an earlier foul on Chelsea keeper Petr Cech by Eduardo.The visitors showed why they boast the top-flight's meanest defence as they continually thwarted Arsenal to deny them any clear-cut chances.It was a defensive performance the home side might do well to take note of as they seek to add the steel to their style that many critics argue they lack.The Gunners were also clearly feeling the absence of injured striker Robin van Persie, who had scored two goals in a victory over Chelsea this time last year, as they lacked a cutting edge to their play.And the home side almost fell further behind in bizarre circumstances.A Drogba strike ricocheted off both William Gallas and Frank Lampard and was set to creep into the bottom corner before Almunia, at full-stretch, palmed the ball wide.But Drogba continued to prove a chief tormentor for Arsenal as he beat Almunia with a free-kick which gave him his 11th Premier League goal of the campaign and 14th in total.It was three points earned with authority from Chelsea and proved the show of strength from them that Wenger was looking for from his own side.Source: BBC