Arsene Wenger conceded Arsenal suffered a "nightmare" after Bayern Munich hammered them 5-1 in their Champions League round-of-16 first leg clash at the Allianz Arena.
The Gunners looked like addressing their recent poor form at this stage of the competition, where they have been eliminated in the past six years, after a spirited reaction to falling behind to Arjen Robben's early strike.
Alexis Sanchez saw a penalty saved before tucking home the rebound as the sides went in level at the break, but the second-half capitulation saw Bayern steamroller their visitors as a Robert Lewandowski header, a Thiago brace and a late Thomas Muller strike put Carlo Ancelotti's side firmly in the driving seat to qualify for the quarter-finals.
The result only increases the question-marks over Wenger's future, with his contract expiring in the summer and a growing number of fans calling for change.
Arsenal shipped three goals in 10 minutes and all within 15 minutes of losing captain Laurent Koscielny to injury, and a downbeat Wenger admitted after the game his side had become "vulnerable" as the night progressed.
"It's difficult to explain," he told BT Sport.
"Just before half-time we had two good chances to score. We came back and played well. In the second half we lost Koscielny very quickly - he came off at 1-1 - and finally we collapsed.
"It's difficult when we collapsed - and Bayern were the better team as well. I felt the third goal was a killer for our players because after that we had no response.
"The real problems were after the third goal. We lost our organisation and we looked mentally jaded and vulnerable from that moment onwards. The last 25 minutes was a nightmare for us."
Wenger also agreed that his side now require 'miracles' to make the last eight, and will be pouring over the footage in search of why his defence fell to pieces as Bayern ran riot.
"The two goals (second and third) were difficult to swallow - 53 and 56 minutes," he added.
"We have to analyse that. It looked like we lost our organisation. Not only did we lose our centre-back, but a combination of mentality and organisation. Before that, we controlled them quite well."
Ancelotti, who has been under a little pressure despite Bayern sitting seven points clear at the top of the Bundesliga, saw his side break a Champions League record as they recorded their 16th consecutive home win.
But the former Chelsea and Real Madrid boss refused to say the tie was over ahead of the return leg at the Emirates Stadium on March 7.
"The performance was good," he said.
"We played really well, but as I said, it's not the final. We need to play the second game unfortunately.
"The result is really important, but we don't want to make a mistake. We have an advantage but we have to prepare the next game in London.
"We want to play like we did tonight - same intensity, same spirit, same concentration. We want to avoid problems."