Another season, the same old way to fail. Arsenal have a particular way of losing games and all the familiar tropes were there in abundance on Wednesday: the squandered chances, the needlessly complicated attacking moves, the lack of urgency, the defensive laxity. Arsène Wenger seemed wearily resigned after the game, which is hardly surprising – he has done the press conference over and over again. The difference is, this wasn’t Barcelona or Bayern Munich inflicting the defeat; it was Monaco.

Seemingly going out of his way to avoid using the term, Wenger effectively confirmed he felt his side had been complacent but that charge of underestimating Monaco applied to his tactical set-up as much as anything. When Arsenal beat Manchester City at the Etihad in mid-January, they were arrayed in a 4-3-3, Francis Coquelin flanked by Santi Cazorla and Aaron Ramsey. Here, it was a 4-2-3-1, which, willing as Cazorla was, simply did not offer sufficient protection for the back four.

What was extraordinary was what willing victims Arsenal were. These were failings seen a thousand times before, familiar enough to obliterate the sense engendered after the victory at Manchester City that somehow a new, grittier Arsenal had been forged from the long history of past mistakes. There was a staggering naivety about Arsenal’s play, so they resembled a team that had never played in a two-legged tie before.

Monaco were solid, sitting a screen of three players in front of the back four, and clinical on the break – but no more than that. The finishes of Dimitar Berbatov and Yannick Ferreira-Carrasco were superb but other than that Monaco offered nothing particularly beyond what would be expected of a competent side that had conceded only two goals in its previous 12 games.

This was a story of Arsenal failing to fulfil the basics. It was as though their domination of possession in the opening minutes – they had more than 90% of the ball for the first five minutes – lulled them into a sense that this would be a game of attack against defence, that somehow the basics no longer applied.

When Danny Welbeck lost possession on the halfway line on the left there was a general sluggishness about covering. As João Moutinho received the ball in space, Cazorla was forced across, which in turn left Geoffrey Kondogbia unmarked. He had time to take a touch and measure his shot. Wenger was right to say there was bad luck in the way it deflected off Per Mertesacker on its way in but it is also true that had Mertesacker not turned his back, had he not been the closest defender to Kondogbia 10 yards away, there wouldn’t have been a chance for misfortune to take effect.

The second and third goals were even worse, so bad that even Wenger admitted they were “suicidal”. Fabinho deserved credit for the way he battled almost to the halfway line after picking up the loose ball but when he slipped a pass through to Anthony Martial, Arsenal’s defence melted away, the full-backs caught high upfield, so that he had the simplest task to roll the ball inside for Berbatov to score with relish and elan.

That might have been a warning and yet when Arsenal had got back into the game at 2-1, they were caught again. Alex Oxlade-Chamberlain was dispossessed and must bear some of the responsibility but again the defence behind him vanished as the ball was worked to Ferreira-Carrasco. “The heart took over the head,” said Wenger – which may be true but it shouldn’t really be an excuse. This is Arsenal’s 17th consecutive season in the Champions League: they of all sides should not be making neophyte’s errors – but there had been issues throughout.

A look at the heat maps showed just how narrow Welbeck and Alexis Sánchez ended up playing, they and Olivier Giroud forming a tight triangle. Quite apart from the fact that meant Monaco’s defence was never stretched, it also meant that they were always able to play the ball out through the full-backs. That hinted at a much bigger question: can Sánchez and Mesut Özil play together?

In theory, the hyperactive charging of Sánchez and the more languid stylings of Özil should complement each other but perhaps they are simply too different. Certainly, when both play in a 4-2-3-1 the sense is of a team tipped too far towards creativity, lacking defensive responsibility.

Although Cazorla has taken a deeper role over the past season, Arsenal effectively played with six attacking players. With a coherent pressing structure, that is – just about – achievable but nothing Wenger has done in the past decade has shown him capable of drilling a team to press with the mutual understanding Bayern Munich, Barcelona, Borussia Dortmund or even Southampton do.

Without that the selection smacked of the word Wenger was so determined not to use: complacency.