Arsenal are in danger of an embarrassing exit from the Champions League after Monaco romped to a stunning 3-1 win in the last 16 first leg at the Emirates Stadium on Wednesday.
Arsene Wenger's team were left shell-shocked as Geoffrey Kondogbia put the French club ahead with a deflected first half strike before former Tottenham forward Dimitar Berbatov marked his return to north London with the second goal after the interval.
Berbatov's cool finish was a hammer blow to the Arsenal fans who had jeered him for his past allegiance to their bitter rivals and there was worse to come.
Alex Oxlade-Chamberlain had just given Arsenal renewed hope with a 90th minute goal when Yannick Ferreira-Carrasco galloped clear to score Monaco's third and leave the Premier League team needing a herculean effort in the second leg on March 17 to avoid last 16 elimination for a fifth successive season.
It was an especially chastening evening for Wenger, who made his managerial reputation during a seven-year spell at Monaco and was renewing acquaintances with his old club in a competitive match for the first time.
"The third goal makes our task extremely difficult in the second leg. It looks like we lost our nerve and our rationality on the pitch," Wenger said.
"The heart took over the head and that doesn't work. Mentally we were not sharp enough to get into the game and we paid for it."
Leonardo Jardim's side produced a counter-attacking masterclass to leave Arsenal impotent in attack and incompetent in defence and the Monaco coach said: "Arsenal have some excellent individuals and we were able to nullify their threat.
"Nobody really thought this result was possible but we achieved it."
Alexis Sanchez has emerged as Arsenal's creative fulcrum in his debut season and the Chile winger almost found the key to unlocking the obdurate Monaco rearguard when he exchanged passes with Mesut Ozil before flicking his shot just over.
But, emboldened by the ease with which they had kept Arsenal at bay, Jardim's team began to push forward with more confidence and Joao Moutinho found space for an acrobatic volley that sailed over.