Former Tottenham striker Dimitar Berbatov returned to haunt Arsenal as Monaco secured a 3-1 win in the first leg of their last 16 Champions League tie at the Emirates Stadium.
The French side, whom Gunners boss Arsene Wenger guided to the Ligue 1 title in 1988, had been viewed as one of the weaker seeds for the knockout stages, but proved anything but as Arsenal failed to get out of first gear and were punished as Olivier Giroud had a night to forget, missing several good chances.
A 25-yard deflected effort from Geoffrey Kondogbia put Monaco ahead on 38 minutes, and after Giroud had spurned another two great chances to get his side level, Berbatov crashed in a second on the break.
Substitute Alex Oxlade-Chamberlain, returning from a groin injury, grabbed Arsenal a lifeline in stoppage-time only for Yannick Carrasco to slot home a third away goal on the break which leaves Arsenal facing exit from Europe before the quarter-finals once again.
It had earlier been a positive start, as Danny Welbeck, preferred again to England team-mate Theo Walcott, got ahead of Elderson and into the Monaco penalty area, but curled an angled shot just over.
Mesut Ozil was appealing for handball as Brazilian defender Wallace came across to shepherd a long pass up field out for a corner – with replays showing the German may well have had a case despite it being missed by both the referee and his assistant behind the goal.
Monaco – who had conceded only twice in the last 17 matches – looked to hit Arsenal on the break with the 34-year-old forward Berbatov, who left Fulham to join Monaco in January 2014, the main outlet. He was roundly jeered by the home fans but would have the last laugh.
When the Gunners did manage a to briefly rally, Alexis Sanchez had to dig the ball out from behind him 18 yards out, and floated it just over the crossbar.
Joao Moutinho's volley flew high off target after a break down the left, before Monaco took an unexpected lead on 38 minutes.
The ball was moved inside to Kondogbia some 25 yards out, and his shot took a big deflection off Per Mertesacker and flew past David Ospina.