Well, that was absolutely baffling and brutal to watch for Arsenal fans.
In truth, the Gunners cannot complain about the result as their performance gave them what they deserved - they probably didn't even deserve a consolation goal!
It was such an 'Arsenal' performance that you couldn't help but laugh; from Alex Oxlade-Chamberlain's lifeline in the dying minutes to the same man costing Arsenal in the dying seconds to gift the Ligue 1 outfit a third goal and all but killing off the tie.
Nothing went right for the boys of north London, epitomised by the fact Dimitar Berbatov, one-time hero of their arch rivals Tottenham Hotspur, found his name on the scoresheet.
If Arsenal are going to comeback from a 3-1 defecit, then there aren’t too many better teams to face in this competition, however, the fact only six teams in European cup history have gone through after a first-leg defeat, I wouldn’t bank on a footballing miracle.
Anyway, here’s what we learnt from tonight’s clash at the Emirates.
Walcott's Arsenal career over?
Theo Walcott was yet again on the bench for Arsenal tonight and although the Englishman has the most appearances and goals of anyone in the current squad, that lengthy spell on the sidelines appears to have cost him dearly.
Arsene Wenger opted to go for Danny Welbeck alongside Alexis Sanchez and Olivier Giroud in the final third and with Alex Oxlade-Chamberlain also returning to the squad tonight, you have to question just how long Theo's Arsenal career will last.
Arsenal have their Patrick Vieira replacement
Well, kind of. They don't own him but boy should Arsene Wenger do everything he can to make sure they do. Geoffrey Kondogbia put in an imperious and physical performance in the middle of the park, capped off with his fine opener (via a helping hand from Per Mertesacker).
It is hard to replace someone of Patrick Vieira's talents, however, Arsene Wenger could go a long way in doing so by bringing the former Sevilla midfielder over to the Premier League.
Time for Gabriel
Per Mertesacker was at fault for two of Monaco's three goals tonight, sure, it is hard to blame the former German international for the first goal - a wicked deflection - however, shouldn't he close down Kondogbia quicker?
The blame can firmly be placed at Mertesacker's door for the second, though, with the central defender's rash decision to close down Monaco on the halfway line backfiring majorly, leaving Dimitar Berbatov to run through unmarked and to smash home.
Arsenal never really change
They always do it, Arsene Wenger's side always trick the footballing world into thinking they're ready to return to the upper echelons of English football. And then they go and do things like trail Liverpool 4-0 after 20-minutes or throw away a 3-0 lead at home to a bang average Anderlecht.
North London derby performance aside, Arsenal's recent form had been impressive and they were expected to coast past Monaco tonight, have the job done after the first-leg. However, the footballing version of suicide is never too far away from this group.