Spain playmaker Juan Mata scored one goal and set up another as Chelsea handed Arsenal its first loss of the season, winning 2-1 on Saturday to consolidate top spot in the Premier League.
Mata's curling free kick that glanced off Arsenal defender Laurent Koscielny into the net proved to be the winner in the 53rd minute, earning the European champions a fifth win in six league games and dealing a blow to one of their potential rivals for the title.
So solid at the back this season, Arsenal's defensive vulnerability returned at Emirates Stadium, looking unsure at set pieces with Fernando Torres beating Koscielny to another free kick by Mata to give Chelsea the lead in the 20th.
''Defensively, we were not at the level we have to be in a game like this,'' said Arsenal manager Arsene Wenger, who may regret the decision to play Koscielny ahead of the in-form Per Mertesacker.
The spotlight was also on a center back for Chelsea, with John Terry playing just two days after being banned for four games for racially abusing an opponent in a league game last year.
With the defender contemplating whether to appeal the suspension, he remained available for Chelsea and shrugged off constant jeers from the home fans to deliver a largely composed display.
Terry was fooled by the good movement of Gervinho for Arsenal's equalizer in the 42nd, however. The Ivory Coast international peeled off the former England captain before controlling a cross by Alex Oxlade-Chamberlain and slamming an unforgiving close-range finish high into the net, maintaining his improvement this season after being handed the center-forward berth by Wenger.
That was the first goal that Chelsea had conceded in four games but Roberto di Matteo's side held on to secure victory in its toughest test yet this season, proving it has the mettle in defense and creativity up front to challenge the two Manchester clubs for the title.
''I'm very pleased today with our performance,'' Di Matteo said. ''We played against a very good team and we didn't allow Arsenal to get in a rhythm.''
Terry ran over to the jubilant Chelsea fans after the final whistle, clapping their raucous support and slapping the badge on his jersey before handing one of his boots to a young boy. Every touch of his was booed but he is used to such abuse.
''I think it was the right choice to pick him today,'' Di Matteo said. ''He showed his leadership qualities and what a good defender he is.''
It was Arsenal's first setback of an otherwise encouraging start to the campaign, leaving them seven points behind Chelsea, and the blame for both goals could be apportioned to Koscielny, who allowed Torres to hook his right foot around the France defender to score at the far post.
Koscielny was fortunate not to give away a penalty three minutes later after being sloppily dispossessed by Torres and then possibly nicking the striker's foot as he bore down on goal.
And for Mata's goal, Koscielny dived in to try to clear the set piece, but the ball glanced off his leg into the net and left goalkeeper Vito Mannone stranded.
''I feel we played against a good team but we gave the game away,'' Wenger said.
After starting sluggishly, Arsenal only really came to life following the introduction of Oxlade-Chamberlain in the 17th after the injury-prone Abou Diaby hobbled off with a thigh strain that Wenger said will rule the France midfielder out for three weeks.
But Chelsea looked dangerous on the break through Torres, Mata and Eden Hazard, and conceded few clear-cut chances. Santi Cazorla, the diminutive playmaker who has been at the center of everything good about Arsenal in its first five games, was often crowded out by combative Chelsea midfielders John Obi Mikel and Ramires while forward Lukas Podolski was quiet all match.
When the opportunities came for the hosts, Chelsea goalkeeper Petr Cech did well first to claw away Podolski's header in the 59th and then palm aside a deflected effort by Olivier Giroud, Podolski's replacement.
In second-half injury time, Giroud had a great chance to secure a draw for Arsenal but having rounded Cech, he fired into the sidenetting.
''I'm really pleased with the way we played away at the Emirates,'' Di Matteo said. ''We've made a great start to the Premier League. Hopefully we can be there at the end.''
