FC Schalke 04 retained their hold on top spot in Group B after coming back from two goals down to draw 2-2 at home to Arsenal FC.
Vanquished in London on matchday three, the visitors looked set to redress the balance after Theo Walcott's 18th-minute opener was reinforced by Olivier Giroud's maiden UEFA Champions League goal eight minutes later. However, Klaas-Jan Huntelaar's fourth strike of the group stage gave the hosts hope in first-half added time and Jefferson Farfán deservedly levelled midway through the second period. Huub Stevens's side therefore stay a point ahead of their opponents at the summit.
Schalke provided the crisper, more incisive football of the early exchanges and after Vito Mannone had turned aside an Ibrahim Afellay shot, a Benedikt Höwedes header flashed just over. However, it was the head of another Schalke player, Roman Neustädter, which brought the breakthrough. Stretching, the midfielder could only help on Per Mertesacker's forward pass, and though Giroud's charge towards goal was halted by a lunging Höwedes, Walcott snapped onto the loose ball to finish.
The north London outfit soon doubled their lead. Having only just come off the bench to replace the injured Atsuto Uchida, Marco Höger unsurprisingly looked stiff-limbed as Lukas Podolski turned away from him and crossed for the unmarked Giroud. Having made the challenge that initially kept the attack alive, the former Montpellier Hérault SC forward deserved plaudits for more than just his headed finish.
Schalke took their time to recover, yet found respite with the last kick of the first half. When Santi Cazorla tripped on the ball, the Bundesliga team pounced, Lewis Holtby cleverly finding Huntelaar, who steadied himself before drilling low across Mannone. Had the Dutch international finished as deliberately five minutes after the break, Schalke would have been level, but he fired straight at Mannone after stealing in behind the visitors' back four.
A Mannone save from Holtby's drive and Mikel Arteta's block on the line from Höger's shot preserved Arsenal's advantage. However, Schalke finally found a way through when Afellay's long cross from the left reached the unmarked Farfán, whose angled effort ricocheted into the net off Thomas Vermaelen.
Walcott might have proven a late hero for the Gunners when he muscled past Joel Matip with seconds left, though he could only shoot meekly at Lars Unnerstall to leave the section finely poised with two games remaining.