The pressure on Arsenal manager Unai Emery intensified as Daichi Kamada's brilliant double earned Eintracht Frankfurt victory at the Emirates Stadium.
The Gunners boss came into this Europa League match having failed to lead his team to victory in their previous six outings, and this latest defeat means this is their longest winless run since February 1992.
At full-time the Spaniard appeared to make a gesture to the sparse home support as they jeered him, with some holding 'Emery Out' posters having watched their side surrender control against a team who were a clear second best in the first period.
However, Arsenal will seal qualification for the last 32 if they avoid a heavy defeat at Standard Liege in their final Group F game.
It looked like the Gunners had turned the corner after they dominated the opening period. Eintracht spent most of it trying to keep Arsenal's attack at bay until Pierre-Emerick Aubameyang made the breakthrough with a strike just before half-time.
The Bundesliga side only managed one shot on goal in the first half, but were transformed after the break and equalised when Kamada curled in a fierce effort from the edge of the box.
The 23-year-old Japan international then put his side in front with another sweet strike from the edge of the area.
The contest also marked the return of Granit Xhaka to the Arsenal XI. The Swiss midfielder had missed the Gunners' past five matches after his infamous substitution in the 2-2 draw against Crystal Palace at the end of October, when he angrily gestured to supporters.
The 27-year-old appeared to pick up a knock to the knee in the first half but following treatment played the full 90 minutes.
Unai Emery's Arsenal are 19 points behind Premier League leaders Liverpool
The 48-year-old, given the task of moulding a new Arsenal after succeeding Arsene Wenger in 2018, is now odds-on with some bookmakers to be the next Premier League manager to lose his job.
The Europa League had offered some respite from the difficulties of the top flight - where his side have only won four of their 13 games and are eight points adrift of the top four - but the same problems reared their head on a forgettable night at Emirates Stadium.
With Wolves manager Nuno Espirito Santo identified as a potential replacement, how many more disappointments will Arsenal's hierarchy tolerate before they finally sack him?
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