Arsenal conceded a late equaliser to Vitoria Guimaraes when Bruno Duarte scored a 91st-minute goal for the Portuguese Club.
The Gunners had maintained a 100% record in this season’s Europa league until the match with Vitoria which ended in 1-1 draw.
Shkodran Mustafi scored a late lead for Arsenal from Nicolas Pepe’s free kick.
Guimaraes fought back in the 90+1 minute when Duarte shot into the confused Gunners’ net from former Spurs player Marcus Edwards’ cross from the right.
This will be the fourth consecutive time that Arsenal will fail to hold their lead in all competitions.
It is also a turbulent week for the Gunners as Granit Xhaka was stripped of his captaincy for insulting fans on Sunday’s match with Crystal Palace that saw the game end in 2-2 draw.
Arsenal will still qualify for the final 32 Europa league on Thursday if Standard Liege who are currently in the third place lose to Eintracht Frankfurt in Group F.
Europa League Group F Standing
|R. Standard de Liège||3||1||0||2||3|