Defender Per Mertesacker warned Arsenal must quickly learn how to regain their dynamic style at the Emirates Stadium to salvage any hope of staying in the Champions League.
The Gunners slumped to a 3-2 home defeat against Olympiacos on Tuesday night, when stand-in goalkeeper David Ospina dropped a corner over the line as the Greeks went on to record a first win in England at the 13th attempt.
Arsene Wenger's squad are now bottom of Group F, having lost their opening two Champions League games for the first time, and are in real danger of failing to sustain their record of making it to the knock-out stages for the past 15 seasons.
Arsenal next face a daunting double header against pool leaders Bayern Munich.
German World Cup winner Mertesacker believes the players can regroup to produce the required response, provided they take on board the harsh lesson of Tuesday night, when Arsenal allowed Olympiacos to move 3-2 ahead less than a minute after they had drawn level.
"At home we should be much more aggressive from the start and be more dynamic. That is what our game is all about, possession, but also dynamic-wise we should do much better, with the tempo and the speed," said Mertesacker, who turned 31 on Tuesday.
"We need to come back to that if we want to be more successful in the Champions League and to qualify, we need to do much better.
"When we play like we did (on Tuesday), with that lack of concentration and discipline, then we have got no chance.
"Everyone is disappointed, but we will get up and fight for a minimal chance (of qualification).
"We play Bayern Munich twice in a row and that is a big chance for us to show what a great team we are.
"We have to prove that we can show up with another performance, to play more aggressive, be more direct to the goal and be more convincing."
Arsenal host Barclays Premier League leaders Manchester United on Sunday.
Petr Cech is expected to be back in goal, with Wenger indicating the summer signing from Chelsea was carrying a minor injury concern following last weekend's win at Leicester.
Centre-back Laurent Koscielny was forced off in the second half against Olympiacos after looking to have picked up a hamstring injury while making a slide tackle, so will be assessed.
Mertesacker hopes the Arsenal players can use their shortcomings on Tuesday as a positive in the build-up to the United clash.
"We have got a couple of days to look back on that performance. I think everyone will have regrets and it is good to take that away," Mertesacker said to Arsenal Player.
"It will take a couple of days to recover and to think about Manchester United and play in a different competition, which will be a good opportunity to come back to the Emirates and play our football with possession and dynamism."
