The pressure on Arsenal manager Unai Emery intensified as Daichi Kamada's brilliant double earned Eintracht Frankfurt victory at the Emirates Stadium.
Emery came into this match having failed to lead his team to victory in their previous six outings.
And the way the Spaniard's side surrendered control in the second half of their penultimate Europa League Group F game is likely to cause further concern.
Emery's side will now have to avoid defeat at Standard Liege to be certain of a spot in the last 32.
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 old foe Pierre-Emerick Aubameyang made the breakthrough with his 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.
He appeared to pick up a knock to the knee in the first half but following treatment played the full 90 minutes.