Arsenal suffered defeat to Bayern Munich at the Emirates Stadium in a crazy game in which both sides missed penalties and Wojciech Szczesny was sent off.
Toni Kroos scored the decisive goal early in the second half before Thomas Mueller all but killed off Arsenal's chances in the dying minutes to give Bayern a win which leaves Arsenal with virtually no hope of progressing to the quarter-finals.
Bayern almost got off to the perfect start through Toni Kroos as the German lashed in a brilliant effort from range in the opening minutes, but Szczesny pulled off a fine save to tip it around the post.
Yet it was Arsenal who would enjoy the better start, with surprise starter Yaya Sanogo having a quick flurry of chances, first almost getting on the end of a cross before drawing a fine save from Manuel Neuer after some good supply from Jack Wilshere.
Bayern were looking rusty, with their offside trap in particular failing to function, and Arsenal had their big chance just afterwards -- Mesut Ozil burst past Jerome Boateng and was brought down by the former Manchester City man for a penalty. The umlauted one stepped up to take it and face his former schoolmate in goal, but a nervous-looking stuttering run-up preceded a rather weak effort, which Neuer stuck up a glove to deflect away from goal.
That was a blow to Arsenal's morale, and although the Gunners continued to be on top, Bayern gradually worked their way into the game as the hosts inevitably dropped off from their ferocious pressing. Per Mertesacker averted one moment of danger by blocking an Arjen Robben effort, but disaster was soon to follow for the hosts.
Kroos, who was probably looking like Bayern's best player, floated a fine ball over the top which caught Nacho Monreal, who had just come on to replace the stricken Kieran Gibbs, off-guard and allowed Robben to spring clear of the Arsenal backline. Szczesny raced out to stop him, but Robben chose to bring the ball under his control rather than go for goal or attempt to go around the keeper, leaving the Pole with no option but to crash into him with his momentum. A penalty and a clear red card.
David Alaba stepped up to take it, but incredibly, punted it against the left post for the second missed penalty of the first half, much to the relief of Arsenal and the substitute Lukasz Fabianski. That ended up being the last significant action of a bizarre half of football.
Pep Guardiola shuffled his deck at half-time as he reverted Philipp Lahm to midfield, bringing Rafinha on in place of Boateng and shifting Javi Martinez to centre-back. But it was Arsenal who had the first real chance through a surprising source, however, as Bayern Munich continued to look shaky at the back. Laurent Koscielny, of all people, galloped forward but couldn't quite get the ball under his spell with his first touch and Neuer easily gobbled up the ball.
Robben almost punished Arsenal thereafter with a classic cut-in-and-curl-it effort, but Fabianski did well to both save and hold onto it with Mario Mandzukic lurking. Just afterwards, he almost repeated the trick, but this time the ball ended up at the feet of Kroos on the edge of the area -- and his effort was even better than his early strike, driving an unstoppable effort into the top corner.
Robben was looking dangerous and almost doubled Bayern's advantage just afterwards after bursting down the right wing, but his volleyed shot-cum-cross was shovelled away by Szczesny before it could reach either Mandzukic or the far corner.
Bayern continued to look for goals, but struggled to find them. Robben saw another archetypal effort go just wide, before Mertesacker carried out another great block to deflect Mario Gotze's diving header away from danger. Just afterwards, Koscielny was fortunate to get away with a clear foul on Mueller in the area as he took away the German's legs.
Some brilliant interplay between Gotze and Alaba then left the German with space to shoot, but his effort was tame and Arsenal managed to survive once again, despite dropping ever deeper and seeing fewer and fewer of the ball. Arsenal players were now becoming increasingly frustrated, including with each other, Mathieu Flamini shouting and shoving Ozil for the German's lack of defensive work.
Just before added time, however, Arsenal suffered disaster again as Mueller added a second which will leave their second-leg hopes even slimmer, as the young German peeled away from his marker to head home and double Bayern's advantage.
Claudio Pizarro was close to adding a third, before Kroos struck the post again in injury time, but Bayern couldn't quite finish off Arsenal -- they've certainly come close though, and the Gunners will be facing an almost impossible task in the second leg.
Arsenal: Szczesny, Sagna, Mertesacker, Koscielny, Gibbs (Monreal 31'), Flamini, Wilshere, Oxlade-Chamberlain (Rosicky 74'), Ozil, Cazorla (Fabianski 39'), Sanogo.
Bayern Munich: Neuer, Lahm, Boateng (Rafinha 46'), Dante, Alaba, Thiago (Pizarro 79'), Javi Martinez, Robben, Kroos, Gotze, Mandzukic (Mueller 64').
Goals: Kroos 54', Mueller 88'