Arsène Wenger had insisted beforehand that Arsenal's situation was "not dramatic" yet this is a team that seems to trade exclusively in the commodity. There was the familiar cocktail of hope and anxiety here, together with headline-grabbing plotlines, chief among them Theo Walcott's goalscoring return to the starting lineup for a big game.

Olivier Giroud's headed goal was another highlight while it sounded as if André Santos, the villain of Saturday's defeat at Manchester United, had been booed by some of the travelling fans upon his introduction as an injury-time substitute.

Arsenal started poorly only to take charge when Schalke lapsed for a period in the middle of the first half. Yet Wenger's team lacked ruthlessness and they surrendered the initiative when they conceded in first-half injury-time to Klaas-Jan Huntelaar, which reshaped the tie anew.

They could be relieved that Schalke's second-half plunder extended no further than Jefferson Farfán's equaliser. They came under severe pressure and that the goalkeeper Vito Mannone was their outstanding performer told its own story. And yet, with the very last act, Walcott streaked clear and, with only Lars Unnerstall to beat, he shot straight at the goalkeeper. His goal had taken his season's tally to eight from four starts in all competitions. In a performance that veered from the frustrating to the encouraging and back, there would be no sensational finale.

Arsenal had arrived on the back of the dispiriting defeat at United and scarred by the recent losses at Norwich City and at home to Schalke. This was another rocky ride but the conclusion was positive. It will irk the travelling support that what should have been an unassailable lead was frittered away but Schalke did not deserve to lose. Wenger would surely have signed up for the draw at kick-off time and, indeed, at any point after Farfán's goal and until the last-gasp Walcott chance. Arsenal remain favourite to emerge from Group B, even if they might not do so as top seeds.

Walcott had entered the game as the club's top scorer this season and if there had been a few sniffs about the bulk of his return coming in the League Cup, there was a priceless quality about his early strike. Roman Neustädter erred with a loose back header that put Giroud clean through and although he was dispossessed, Walcott had followed up and, after forcing a break past Unnerstall, he rolled into the empty net.

The goal had come against the run of play, with Arsenal's tweaked backline, that featured Thomas Vermaelen at left-back in place of the hapless Santos, coming under early pressure. Schalke's speed on the break had been a feature of their 2-0 win in London and they gave warnings here when first Christian Fuchs saw a shot deflected wide and then Ibrahim Afellay burst forward to draw a smart save from Mannone. Benedikt Höwedes also flashed a header over the crossbar.

Walcott's goal had a fortifying effect and Arsenal's second was a beauty. Lukas Podolski, booed by the home crowd at the outset, beat the substitute Marco Höger to cross and Giroud thudded his stooping header home. It felt like an old-fashioned goal. Arsenal had the chance to take charge. Schalke, the clinical counter-attackers, were asked to force the issue and the crowd at this cavernous arena had begun to grumble. Yet Wenger's team allowed the hosts to fashion a lifeline. Farfán had gone close with a rising drive and Giroud headed straight at Unnerstall when Lewis Holtby's header froze the Arsenal defence. Huntelaar's finish was low and true.

Wenger could be concerned at the number of chances that his team permitted Schalke and the hosts dominated the second half. Vermaelen's positioning was suspect and there was a fretfulness about Arsenal at the back. At no point, even at 2-0, did they look secure and this formed the basis for the post-match criticism.

The pattern became entrenched. Schalke pushed forwards, with Holtby instrumental and Arsenal attempting to cling on. Mannone denied Huntelaar one-on-one; Arteta smuggled a Höger shot clear and Mannone parried Holtby's swerving drive. The equaliser had been trailed and it arrived when poor marking at the far post allowed Holtby to flick on and Farfán's drive to fly in, despite Vermaelen's efforts to clear.