Arsene Wenger has admitted that his side made "big mistakes" in the 2-0 defeat to Bayern Munich at the Emirates Stadium on Wednesday night.
Arsenal missed an opportunity to break the deadlock when Mesut Ozil saw his penalty saved by Manuel Neuer and the hosts were dealt a further blow as Wojciech Szczesny was sent off before the interval.
Wenger admits that those errors cost his team, who now face a battle to reach the quarter-finals of the Champions League.
"We made big mistakes, but the spirit was absolutely fantastic," the Arsenal manager told Sky Sports News. "The penalty we missed killed the crowd and positive vibes. We were down to 10 men and we suffered physically.
"It is a night the team showed some quality, but at the end of the day we lost the game.
"We won at the Allianz Arena last season, we will have to try and do the same again."
Arsenal take on Bayern in the second leg on March 11.
