France international Geoffrey Kondogbia handed the visitors a first-half lead in north London after the midfielder’s long-range effort was deflected past Arsenal goalkeeper David Ospina.
When you’re losing the game, that’s when you need to get to the side of the pitch and tell your players what to do and where to go
Former Tottenham striker Dimitar Berbatov doubled the away side’s first-leg lead, and although Alex Oxlade-Chamberlain scored a 90th-minute effort, Monaco sealed a 3-1 aggregate lead in the last-16 tie thanks to Yannick Ferreira-Carrasco last-gasp strike.
Robson, who made 150 appearances for the Gunners, likened the Arsenal players to “lost sheep” after a hapless display against the Ligue 1 side, criticising Wenger for his performance on the night, too.
“There was just a lack of organisation and understanding as a team, it was absolutely shocking,” Robson told talkSPORT.
“They made some bad defensive decisions because they haven’t worked on it in training, and that wouldn’t happen if they did defensive work day-in, day-out.
“George Graham did that and Jose Mourinho does that, but Arsene Wenger doesn’t, and that’s what you get.
“If you haven’t got a defensive strategy or a team structure, you get individuals chasing around the pitch like lost sheep and that’s what happened against Monaco, it was unbelievably bad defending from Arsenal.
“Even at 2-0 down, you’d think they would try and press the ball and win it back quickly, but they couldn’t get near anybody because they were playing as individuals.
“When you’re losing the game, that’s when your team needs some organisation, that’s when, as a manager, you need to get to the side of the pitch and tell your players what to do and where to go.
“But where’s Wenger? He’s sat there with his hands in his head almost, just watching the game.
“Where is the leadership?”
Gunners do have some hope as manager Wenger has never lost to a Ligue 1 side in France during his Arsenal tenure.
The 2006 Champions League runners-up make the trip to Monaco for the second leg of their last-16 tie on 17 March.
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