Bruno Duarte scored a spectacular goal in stoppage time as Vitoria Guimaraes held Arsenal to a 1-1 draw in the Europa League.
The Gunners led from Shkodran Mustafi's header 10 minutes from time before Duarte levelled with an overhead kick early in injury time on a rainy afternoon in northern Portugal.
Last season's runners-up Arsenal dropped their first points in Group F but lead the way with 10 points.
They will clinch a place in the last 32 if Standard Liege (three points) lose at home against Eintracht Frankfurt (six) on Thursday, with Frankfurt also through in such a scenario.
"I think we could have done better but in the end we have to accept and take the point with us," Mustafi told BT Sport.
"They are a good side. They are in the Europa League for a reason and are quite compact."
Unai Emery's side has struggled domestically lately and also in the first date with Vitoria which they won 3-2 from 2-1 down in the last 10 minutes from Pepe's brace.
Vitoria deserved the equaliser for their first point in the campaign, and could have even grabbed a late winner, with Mustafi deflecting a cross against the outside post of his goal and Rochinha shot just wide.
Arsenal, who were without new captain Pierre-Emerick Aubameyang, his predecessor Granit Xhaka and Mesut Ozil, had no effort on target apart from Mustafi's goal and have now drawn their last four matches in 90 minutes.
The game was brought forward by one day from the regular Thursday slot because Guimaraes' stadium is just 20km away from that of Braga who host Besikats on Thursday when all other games are also played.
Australian Associated Press