Arsenal boss Arsene Wenger accused his players of losing their nerve and blamed “suicidal” defending after a 3-1 home defeat by Monaco left them on the brink of Champions League elimination.
Goals from Geoffrey Kondogbia and Dimitar Berbatov put Monaco in control of the last-16 first-leg tie.
Alex Oxlade-Chamberlain gave Arsenal hope, but Yannick Ferreira Carrasco added a third for the visitors.
“It is just not right to give goals away the way we did,” said Wenger.
“We missed chances and were suicidal defensively.”
Arsenal must now score at least three goals when the sides meet at Stade Louis II on 17 March if they are to avoid exiting at the last-16 stage for the fifth straight season.
No side has lost a European Cup or Champions League first-leg knockout tie at home by two goals and progressed since Ajax in 1969.