It is surely no consolation to Arsenal that their first defeat of the season showed a certain togetherness, as blame for it could be shared throughout the side. There were deficiencies in defence, deficiencies in midfield and deficiencies up front.

Arsène Wenger expressed familiar lamentations about his team's mentality. And supporters were left venting familiar grievances about a club they fear will remain prone to such performances for as long as they spend each new season integrating fresh arrivals to replace departed stalwarts and make do with a squad that never quite looks complete.

Before this match Arsenal announced pre-tax profits of £36.6m for the year ending 31 May, and they are in rude health financially. But the fans' mood is still locked in a debilitating cycle of boom and bust. After the upswing triggered by the impressive win over Liverpool and draw at Manchester City, the sorry loss to Chelsea caused a plunge back towards pessimism. Chelsea did not have to excel to triumph.

"This was a game where everybody said 'OK, this is a real test of how we are doing' and we did well, so that is pleasing." That was the assessment of the Chelsea goalkeeper, Petr Cech: the flip side applies to Arsenal.

The home side's most obvious flaw was not necessarily the most worrying for the campaign ahead. Chelsea's goals came from set-pieces that were badly defended, notably by Laurent Koscielny, who lost his bearings as Fernando Torres guided in the first one in the 20th minute and then, in the 53rd, failed to cut out Juan Mata's free-kick and instead helped it into the net.

"We knew before the game we were playing against a team that was more mobile, more based on movement and played more on the ground and that's why I decided to play him," said Wenger by way of explanation for his decision to deploy Koscielny instead of Per Mertesacker, who had enjoyed a fine start to the season.

In fairness to Wenger, his logic was sound. But Koscielny suffered an off-day. That can happen to anyone but what was more alarming was that his mistakes were aggravated by a lack of communication – Wenger suggested Koscielny's troubles at the first goal were caused partially by the team's failure to reassign marking responsibilities after Abou Diaby was forced off injured three minutes earlier.

Such a laissez-aller approach pervaded this Arsenal performance and that, unlike Koscielny's bungling, is a frequent complaint. "We needed more personality, we were too passive," regretted Wenger. "We needed to attack the ball." That charge could be aimed at the whole team, not just a defence that, until the visit of Chelsea, had shown clear signs of progress since the summer appointment of Steve Bould as Wenger's assistant.

The meekness was perhaps most evident in midfield. Diaby was twice caught dozing on the ball before departing in the 17th minute and, while Santi Cazorla and Mikel Arteta toiled without finding much inspiration, Aaron Ramsey seemed too content to be a passenger. The Wales captain seldom exerts an influence commensurate with the faith placed in him. Up front, there can be no denying that Gervinho exerts an influence. However, even though he struck his fourth goal of the season with a splendid swivel and shot just before half-time, it is by no means clear that the Ivorian's influence is more positive than negative. Against Chelsea, as on countless previous occasions, his decision-making and execution were frequently exasperating, causing chances to disappear in groans.

Theo Walcott, who began on the bench, is accused of lacking a football brain but even he seems to have more reliable instincts than Gervinho. For the season ahead, the forwards on whom Arsenal could find themselves counting the most are Lukas Podolski, who was peripheral to proceedings here, even if one late header did bring a smart save from Cech, and Olivier Giroud.

Not for the first time this season, Giroud perpetrated a miss late in this game that Wenger admitted was "difficult to explain", slashing into the side netting after rounding Cech. That miss means he has scored just one goal in eight appearances since his £13m move from Montpellier.

However, unflattering comparisons with Marouane Chamakh could yet prove unwarranted. Giroud's movement, strength and build-up play suggest he has the skills to be an effective fulcrum and that his barren spell is as unsustainable as Gervinho's prolific one. If he rediscovers his knack for finishing, Giroud could solve one Arsenal problem. But the big Arsenal problem is that the team remains beset by too many 'ifs'.

Man of match Juan Mata (Chelsea)