Arsenal saw goalkeeper Wojciech Szczesny sent off after record-signing Mesut Ozil had missed an early penalty, and eventually went down 2-0 against Bayern Munich in the Champions League last 16 first leg clash at the Emirates Stadium.
There was a blistering start to the European tie - a year on from their last encounter in north London - and the holders could have snatched an early lead when Toni Kroos fired in a 25-yard effort towards the top corner, which Szczesny tipped over.
Yaya Sanogo had been a controversial selection in attack ahead of France striker Olivier Giroud, whose off-field actions have made headlines in recent weeks.
However, the summer free transfer from Auxerre - who has been out for several months with a back problem - saw a close-range shot palmed away by Manuel Neuer, before the German keeper saved a tame spot-kick from Ozil on eight minutes.
There was more drama just before the break as Arsenal goalkeeper Szczesny was shown a red card for bringing down Arjen Robben in the penalty area - only for full-back David Alaba to side-footed his spot-kick against the base of the post.
Bayern, though, went ahead on 54 minutes with a superb 20-yard strike from Kroos, which was whipped into the top corner past substitute keeper Lukasz Fabianski.
Arsenal tired heading into the final 20 minutes as Robben exploited the space in front of a jaded backline.
Eventually, the pressure told as substitute Thomas Muller headed in a late second goal to all but kill off the tie ahead of the return leg at the Allianz Arena next month - where Arsenal won 2-0 last season, but ultimately lost on away goals.