Arsenal's journey has turned down its final cul-de-sac. In truth, there was probably one wrong turn too many before their latest trauma but there is surely no way back for Arsène Wenger's side now, nine points adrift and fast disappearing into Manchester United's wing mirrors with only four games remaining.

They were undone here by a 90th‑minute goal from the substitute Tamir Cohen, flashing a header beyond Wojciech Szczesny to expose Arsenal's seemingly ceaseless vulnerability when defending corners. At that moment Wenger turned away in anguish and hurled his water bottle to the floor. Earlier we had seen him release his pent-up frustration by doing the same with the ball, throwing out his arms in anger. His team had contributed to a game of rich entertainment but once again there was a telling demonstration of the flaws that have brought them to the brink of a sixth successive year without a trophy.

Attacking-wise, they were beguiling at times; defensively, they were bewildering. Their football was slick, penetrative and frequently thrilling, culminating in a frenetic onslaught of the Bolton goal before Cohen's goal. Yet there were other times, particularly in the first half, when their opponents sliced them open with ridiculous ease.

This defeat ends a 16-match unbeaten run in the league stretching back to December but even that was deceptive. Eight of those games had finished as draws, including five of the past six. In all competitions Arsenal have registered one win in their past nine matches.

Wenger may need to re-invent this team if they are to emerge as more credible challengers next season and he will have to start with the side's defence. The frequency with which they switch off when facing set pieces has become as much a part of Arsenal as their red and white strip and, as well as Cohen's winner, it also manifested itself for the opening goal: another badly defended corner, ending with Daniel Sturridge nodding in the rebound after Samir Nasri had blocked Johan Elmander's header on the goalline.

In fairness to Arsenal they were thwarted by some terrific goalkeeping from Jussi Jaaskelainen and some last‑ditch defending – epitomised at 1-1 by Gary Cahill's block to keep out Nasri's goalbound effort – and they also had legitimate reason to believe they should have been awarded a penalty for Paul Robinson's early challenge on Theo Walcott. Kevin Davies was fortunate, too, to last the distance, yellow-carded for one challenge on Laurent Koscielny but let off for a worse offence committed on Alex Song.

Yet it is probably time Arsenal started to focus on their deficiencies and it was not a one-off to see them guilty of wastefulness and, at times, an over-elaborate build-up. The sense of déjà vu was overwhelming – and the same applied to their defensive shortcomings. In many ways it was a performance that symbolised Arsenal's season.

Sturridge, in particular, was a constant menace. Even ignoring his goal, his vision, intelligent positioning and ability to play the killer pass reiterated his credentials as a player of enormous potential. He has now scored seven times in his nine games for Bolton since joining the club on loan from Chelsea and was also involved in the penalty from which Davies should have made it 2-0.

It was, however, a generous decision from the referee, Mike Jones, with Johan Djourou barely making contact with his opponent. Davies's effort was poorly struck and Szczesny's save had seemed as if it could be the defining moment of the game. Within a minute Robin van Persie had exchanged passes with Cesc Fábregas and driven his shot past Jaaskelainen to establish a new Premier League record, the first player to score in seven successive away matches.

What followed was a period of almost unremitting pressure. Fábregas and Jack Wilshere were tremendous in the centre of midfield. Nasri, however, is not carrying the same threat as earlier in the season whereas Walcott, after a bright start, ought to have done more to expose Robinson's lack of pace.

Then came the final, telling blow. Bolton's corner had emanated from a breakaway attack in which Elmander was left clear on goal. After Szczesny had turned away the shot. Taylor swung in the corner and Cohen, on the pitch only five minutes, took advantage of some statuesque defending to leave Wenger howling in anguish.

It was an emotional moment for Cohen, who took off his shirt to reveal a picture of his father, Avi, the former Liverpool player who died after a motorcycle accident in Israel in December. Cohen broke down in tears after the match as he was being interviewed. It put Arsenal's own anguish into perspective but, for very different reasons, their pain was considerable.