Arsenal's hopes of Champions League progress are in serious jeopardy after they slumped to their second successive group stage loss at home to Olympiakos.
Arsene Wenger's side knew nothing other than victory would do after defeat by Dinamo Zagreb in Croatia in their opening game - and with two meetings with group favourites Bayern Munich still to come.
Instead it was a dreadful night for Arsenal, who must now become the first team since Galatasaray in 2012-13 to lose their first two group games and still reach the knockout stage.
The Gunners' display was summed up by the wretched first-half own goal conceded by David Ospina - preferred to Petr Cech in goal - when he dropped Kostas Fortounis's corner into his own net after Theo Walcott equalised Felipe Pardo's deflected shot.
Alexis Sanchez gave Arsenal hope with a 65th-minute header only for Alfred Finnbogason to restore Olympiakos's lead within a minute.
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